Design and experimental study of a novel air conditioning system using evaporative condenser at a subway station in Beijing, China

Accepted Manuscript Title: Design and experimental study of a novel air conditioning system using evaporative condenser at a subway station in Beijing, China Authors: Song Pan, Fei Pei, Hongwei Wang, Jiaping Liu, Yixuan Wei, Xingxing Zhang, Guoqing Li, Yaxiu Gu PII: DOI: Reference:

S2210-6707(18)30609-7 https://doi.org/10.1016/j.scs.2018.09.013 SCS 1251

To appear in: Received date: Revised date: Accepted date:

31-3-2018 8-9-2018 14-9-2018

Please cite this article as: Pan S, Pei F, Wang H, Liu J, Wei Y, Zhang X, Li G, Gu Y, Design and experimental study of a novel air conditioning system using evaporative condenser at a subway station in Beijing, China, Sustainable Cities and Society (2018), https://doi.org/10.1016/j.scs.2018.09.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Design and experimental study of a novel air conditioning system using

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evaporative condenser at a subway station in Beijing, China

Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing

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Guoqing Li d, Yaxiu Gu e

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Song Pan a, Fei Pei a, Hongwei Wang a, Jiaping Liu a, Yixuan Wei b, *, Xingxing Zhang c, *,

Research Centre for Fluids and Thermal Engineering, Department of Architectural and Built

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b

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University of Technology, Beijing 100124, China

Environment, University of Nottingham, Ningbo 315100, China School of Industrial Technology and Business Studies, Dalarna University, Falun 79188, Sweden d

Beijing Institute of Residential Building Design & research Co.,LTD, Beijing 100005, China

Research laboratory of HVAC, college of Architectural Engineering, Chang’an University, Xi’an 710061,China

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Corresponding author1: [email protected] *Corresponding author2: [email protected]

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Highlights

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In this paper, a novel energy-efficient AC system incorporating an independent evaporative condenser (EC) system is comprehensively investigated.

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The most obvious phenomenon is the imbalanced cooling capacity of side A and side B as high and low efficiency working condition. The COP value of high efficiency working condition is 4.0, almost the same as rated

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condition 4.3.

An economic model is applied to analyse the application feasibility and benefits of the EC-AC system against the conventional WC-AC system.

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Abstract

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Air conditioning system (AC) contributes significantly to the energy consumption of

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underground metros. In China, most metro stations are designed with water-cooling centralized air conditioning (WC-AC) system, it has been found that several serious

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problems are brought by this conventional system, such as large space occupying, water leaking, cooling tower noise and low system efficiency. In order to solve these

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problems, a novel energy-efficient AC system incorporating an independent evaporative condenser (EC) has been proposed and installed at Futong metro station

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in Beijing, China. A series of pilot measurements were conducted to analyze the cooling performance and energy consumption of this novel EC-AC system. During the testing period, the average refrigeration efficiency of COP, SCOP and ACOP in A

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and B side is up to 3.8/3.9, 3.4/3.4 and 2.5/2.3. At the same time, some operation problems such as unbalanced working condition have been identified during measurement. The research indicates that such EC-AC system could be a feasible solution to enhance the energy efficiency and reduce the operational costs and carbon emission in metro stations.

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Keywords: Air conditioning; Performance Evaluation; Energy Conservation; Evaporative condenser; Metro station

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Nomenclature coefficient of performance

CS

cost saving, CNY

CR

carbon emission, kg

Subscripts

G

mass flow rate, kg/s

c

H

enthalpy, kJ/kg

I

current, A

P

eclectic power rate, W

PP

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COP

compressor; condenser fan

i

node

in

inlet

payback period, year

out

outlet

Q

cooling power rate, W

p

pump

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voltage, V

s

supply

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1. Introduction With China’s economic increase and urbanization development in recent years, the urban transportation has grown faster under extremely high pressure, which leads to higher energy consumption and corresponding environmental challenges. With large 3

transportation capacity, metro is one of the most effective public transports for easing the traffic pressure and reducing environmental pollution. However, the large investment and high energy costs have seriously restricted its development [1, 2]. In China’s metro system, the mean energy consumption of air conditioning (AC) system accounts for about 35% of the total energy consumption; indeed, the ratio could be much larger in individual metro lines [3]. Because the capacity of AC equipment

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installed in metro station is usually determined by the full-load operation, according to the design code [4]. However, the full-load operation time (usually appears in the

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morning and evening) of AC system is less than 5% of total running time [3], therefore a large amount of energy are wasted.

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1.1 Related work of WC-AC system applied in metro station

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Although there are various AC systems that meet multiple metro-design requirements

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across different climate zones in China, conventional water-cooled chillers and

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cooling towers are employed by most stations as the cold source for the AC system. Specifically, a typical metro WC-AC system is presented in Fig. 1. Due to the large

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dimensions of air duct and cooling/heating load of the station, a station is commonly divided into side A and B with a large surface air cooler in the fresh air duct,

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respectively. The chilled water of both sides is handled in the central WC-AC system located in the side A. The air-cooled cooling tower which provides the cooling water

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for water chiller is usually placed on the ground near the metro stations to. Nevertheless, it is uneconomical for the cooling tower occupies large space in engorges urban cities. Moreover, environmental issues caused by water spill and noise problem from the cooling tower are often complained by the surrounding residents

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and pedestrians. In addition, long-distance delivering of cooling/chilled water (2030m) is inevitable in the conventional WC-AC system, which consumes a large amount of energy for pumping purpose. The energy consumption of water pumps accounts for more than 20% of the total energy consumption in the metro AC systems [3]. With the increasing scale of the going metro lines, energy consumption of AC 4

system will lead to an extreme rise. Hence, it is urgent to explore further approaches of energy-saving AC systems in metro stations. In order to reduce the energy consumption of AC system, numerous investigations have been conducted by researchers. Ahn et al. [5] developed a statistical analysis model to benchmark the energy use intensity of metro stations in Seoul, South Korea;

[2] adopted the frequency conversion technology (FCT) to reduce energy

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their model offered a reference for future design of AC systems in metros. Yang et al.

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consumption of ventilation and AC system in metro stations; they analyzed the

operation condition of chilled-water pumps with FCT and concluded that the variable air volume for station public area was feasible. Kuo and Liao [6] confirmed the

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feasibility of using the groundwater as a steady and clean cold source for AC system for metro stations in Taipei. Fukuyo [7] studied the effect of task-ambient (TA) AC

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systems on the AC loads of a metro station, the thermal comfort of passengers was

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also investigated via application of computational fluid dynamics (CFD) and

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pedestrian-behavior simulations; he claimed that the optimized system arrangement of air-conditioners could improve thermal comfort while simultaneously decrease AC

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loads. Zhao et al. [8] proposed an artificial freezing method that consumes only small amount of energy by combining air-cooling system and a conventional AC system,

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which fully utilized the outdoor low-temperature air in a cold climate region, thus reducing operation cost by 52% and 53.4% and avoiding environmental issues.

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Likewise, natural ventilation from metro tunnel has been optimized to reduce the AC load in metro [9-11]. Ninikas et al. [12] discussed the potential energy saving and reduction of carbon dioxide emission from heat recovery system of underground

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transport tunnels in Glasgow. Marzouk and Abdelaty [13] started to develop BIMbased framework for performance management of metro stations while Casals et al. [14] implemented an intelligent energy management system for underground stations, but their researches haven’t yet involved the innovation of AC systems in metro.

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Although previous researches have investigated a lot of energy saving strategies or technologies of AC systems in metro, such as the renewed design benchmark, the varied frequency of AC equipment, alternative cooling resources, the novel simulation models, the utilization of natural ventilation etc., however, the solutions mentioned in the studies are not able to overcome the problem addressed above, such like limited space, environmental pollutions, noise issue and long-distance delivery etc. Hence,

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there is a need to introduce a novel type of AC system in order to resolve the common problems occurred in WC-AC system. Furthermore, synthetic measurement and

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experimental analysis in more detail are also necessary to assess its performance in metro station.

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1.2 Related work of EC-AC system

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As the energy-efficient and environmentally-friendly equipment [15-17], evaporative

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condenser (EC) is able to replace the bundle of cooling tower and water chiller which

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perform as the cooling resource in the AC system of metro station. The novel concept would be a potential solution to above issues, because it can largely reduce the

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occupied space and cool down the refrigerant directly, getting rid of the usage of water pill, noise issue of cooling tower and energy consumption of extra high-power

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water pump.

There are many researches are conducted to analyze the performance of EC based on

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industry refrigerator [18, 19], air conditioning [20, 21] and heat pump systems [22, 23]. For example, the technology of evaporative cooled condensers has been promoted the same heat transfer efficiency compared to air-cooled equipment with

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smaller area and lower airflow velocity [24, 25]. Hajidavalloo et al. experimentally compared the performance of evaporative cooled condenser with an air-cooled condenser coupled to a split-air-conditioner unit in hot climate region. The results indicated that the power consumption could be reduced and the coefficient of performance could be improved by using evaporative condenser [26]. They also studied a real window-air-conditioner equipped with an evaporative condenser in very 6

hot climate conditions (about 50℃ wet-bulb temperature). By pre-cooling the inlet air, the novel system was proved with higher COP than air-cooled condenser compared with the traditional AC system [27]. Hosoz and Kilicarslan compared the performance of refrigeration employing three types of condensers, including air-cooled, watercooled and the evaporative condenser. However, the system with water-cooled condenser has highest COP and refrigeration capacity [28]. According to the most

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studies mentioned above, EC is able to results in overall significant savings in power consumption [29].

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The physical performance of an EC is complicated because different fluids flow in

different directions within the dedicated system, interacting with each other through heat and mass transfers. Hence, many theoretical calculations and experimental

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validations are proposed to specifically analyze the thermodynamic characteristics.

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For example, Wang et al. conducted an experimental investigation of the performance

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of an air-conditioning system utilizing an evaporative cooling condenser. The results

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indicated an inverse relation between the dry bulb temperature of condenser inlet and the COP. [30]. Additionally, the combined effect of temperature and humidity of

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returned air on the system performance had been investigated by Maria Fiorentino et al. [31]. The maximum reduction of the heat transfer rate, due to an increase of 6% of

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initial relative humidity, results of 30% for the highest dry-bulb temperature. Liu et al. proposed an AC system using dual independent evaporative condensers. Results were

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found that the coefficient of performance increased with the increasing of evaporative water temperature, as well as the air velocity and the water spray rate. Whereas, COP decreased with the increasing ambient air dry-bulb temperature and the compressor

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frequency[32]. Manske et al. developed a mathematical model for an industrial refrigeration system using evaporative condenser. It was found that the head pressures of operating system presented a linear function of the outdoor wet-bulb temperature. Through the proposed optimum control strategy, the annual energy consumption was decreased by 11% [33]. Based on the mathematic models and experimental

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validations, the operating strategies of the refrigeration system and comfort enhance of indoor environment are also investigated [33, 34]. Furthermore, EC has been developed for a long time and the key problem which researchers concern is how to enhance the heat transfer rate of the evaporative condenser [35]. For example, the external thin film cotton layer on the performance of

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the evaporative condenser was investigated by A.E. Kabeel et al. [36] The results shows that the heat exchange has been increased compared to the ones without external thin film cotton layer. Nasr and Salah [37] carried out theoretical and

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experimental investigation on EC with sheet tubes wrapped with cloth. They

concluded that the proposed EC owns the capability to reject heat thirteen times higher than air-cooled condenser. Similarly, corrugated media pad [38], cellulose pad

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[39], as well as cooling pad [27] are also adopted to retrofit the EC system and

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enhance the heat exchange. Additionally, a novel EC where tubes were immersed in a

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water bash has been analyzed by Hwang et al. [40]. The tubes was rotating and

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carrying a thin water film, absorbing the heat from air stream. In order to accurately model thermal behavior of EC, data-driven approach has been

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adopted to predict the performance of refrigeration. Specifically, artificial neural network (ANN) has been widely used to predict various performance parameters of

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the system [41, 42]. In order to collect the data for training and testing processes, a series of experiments with EC system were conducted. Metin et al. predicted the

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performance of an evaporative condenser using both artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) techniques. The results revealed that the ANFIS technique showed a better prediction capability than ANN [43].

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According to an overview on evaporative condenser, evaporative condensers enhance the heat dissipation process by utilizing the cooling effect of evaporation and therefore energy-usage efficiency improved. The operation principles and heat conduction/transfer theory have been investigated thoroughly. 1.3 Research gap and contribution 8

A number of researches have investigated energy-saving strategies for conventional WC-AC system in metro station. However, common operation problems are still remained such like limited space, environmental pollutions, noise issue and longdistance delivery etc. Hence, EC-AC system is firstly introduced as a novel type of AC system in order to resolve these problems. Although there are plenty of studies discuss the application of evaporative condenser in commercial buildings and

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residential dwellings, few researches focus on the feasibility of EC-AC system in a

large-scale underground project [15], such as metro station. Additionally, there is no

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clear answer about saving potentials in aspects of energy, cost, and carbon emission of such EC-AC system applied in metro station.

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In this paper, a novel energy-efficient AC system incorporating an independent evaporative condenser is comprehensively investigated. The evaporative condenser in

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designed in a special placement to fit in the ventilation duct in metro station. The EC-

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AC system is used in a metro station in Beijing, China. Dedicated measurement was

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carried out in order to evaluate the characteristic coefficient for cooling performance (COP) of the EC-AC system. Moreover, a comparison between the evaporative-

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condenser based AC system and the conventional AC system (with water chiller and cooling tower) is conducted by economic and environmental analysis in order to

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assess the energy and socio-economic saving potentials of the novel system. The overall research results would be useful to demonstrate that the EC-AC system could

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become an effective alternative to the existing AC system towards a green and smart metro environment.

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2. Design and operating principle

2.1 Concept design and operating principle

As shown in Fig. 2, the EC-AC metro system consists of five major components, which are the evaporative condenser, the cooling fans (composed of 20 independent fans), the compressor, the thermal expansion valve and the surface air cooler 9

(evaporator). The evaporator is assembled in the air handling unit. The evaporative condenser is set in the exhaust duct of the metro station cooperated with the fans wall located between the fresh air duct and the exhaust duct. The whole system is connected by copper pipe to ensure leak-tightness. What should be mentioned that, both the sensible heat and latent heat of refrigerant are dissipated by recycled cooling

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water, thus the efficiency of whole system is raised. The concrete structure of the evaporative condenser is depicted in Fig. 3. There are

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seven parts in this condenser; they are the motor, the symmetry rotation axis, the

filter, the water-spraying device, the heat exchanger unit, the water-containing plate and the water eliminator. The rotation of the unit is dominated by the motor and the

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symmetry rotation axis. The heat exchanger unit is combined with the fin-tube

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condensing coil and the filler to maximize heat transfer capability.

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Compared to the traditional WC-AC system, the EC-AC system is a refrigerant direct-

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expansion system which is theoretically more efficient and less space occupied. The cooling towers placed on the ground are removed, leading to solutions of noise issue,

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high energy-consumption and water leakiness. Moreover, the condensing temperature is declined due to the direct expansion and the system COP raises up accordingly. In

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addition, the fresh air extracted from the fresh air inlet or the tunnel, is adequately utilized to cool down the recycled cooling water. Therefore, the EC-AC system is

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expected to be an effective solution to energy efficiency in contemporary metro station.

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2.2 Design of pilot project The pilot EC-AC project was constructed in Futong station of Beijing metro line 14. The construction area of the whole station is 19184 m2. The metro structures of side A and side B are illustrated in Fig. 4 and Fig. 5, respectively. As shown in figures, the evaporative condenser is designed vertically rotatable so as to keep an unobstructed

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state in the fire case. In the daily life the evaporative condenser is kept open whereas set parallel to the duct wall in the fire case. As for side A, the AC system consisted of one large surface cooler, three modular air conditioning boxes, two scroll compressors, three screw compressors, one evaporative condenser and one fan wall. The rated power, capacity and size of all the equipment

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are shown in Table 1. The evaporative condenser was considered as an air-cooled heat exchange unit using R-134a coolant instead of the cooling tower and the water chiller

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as the conventional metro WC-AC system. The evaporative condenser was directly placed into the metro exhausting air-duct, as indicated in Fig. 4. While in the

cooling/heating season of metro station, the air valves installed in both air exhaust

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duct and inlet duct are turned their opening degree to 20%, so there is only 20% volume of the fresh air delivered into the surface air cooler from the outside and only

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20% volume of the return air is delivered into the evaporative condenser. Whereas,

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20% volume of the return air delivered into the evaporative condenser could not

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afford the whole cooling load of the space of side A. The fan wall with 25fans installed between the inlet-air duct and the outlet-air duct is utilized to induce the

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remaining 80% volume of air for the evaporative condenser from the inlet duct. The chilled water is delivered to the large surface cooler and the modular air conditioning

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boxes, where 80% of return air and 20% of fresh air are mixed and transported further to air handling unit. The mixed air is finally handled to the supply AC point and

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distributed to the station. The responsible space of side A includes the station concourse layer, the platform layer, the offices and the facilities rooms. The cooled air handled by the large surface cooler is delivered to the station public area, including

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the station concourse layer and the platform layer. The refrigeration cycle is driven by two screw compressors. On the other hand, the cooled air handled by the three modular air conditioning boxes is delivered to the offices and the facilities rooms. As for side B, the AC system only delivers cooled air to the station public areas. Same as side A, the evaporative condenser was installed in the exhausting-air duct and a fan 11

wall with 10 fans was set up between the air inlet duct and the outlet duct to delivered air for the evaporative condenser. One large surface cooler was installed in the air inlet duct. The whole refrigeration is driven by two screw compressors. Both of the evaporative condensers and large surface coolers are designed as an optional model. They could be opened in the metro ventilation season to reduce the windage and keep

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opened in the condition of fire. The schematic profile is shown in Fig 6. Different from the traditional WC-AC

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system where the chilled water is centrally handled in one side, the refrigeration cycle of EC-AC system is undertaken in-place of side A and side B. Hence the temperature of refrigerant is increasing and energy consumption of fluid transportation are

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3. Measurements set up and procedure

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declined.

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3.1 Measurements set up and instrumentation

In order to evaluate the energy consumption of the EC-AC system in the pilot project,

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a series of practical measurements were set up to record key parameters, such as air velocity, dry-bulb temperature, relative humidity of inlet and outlet of the evaporative

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condenser and surface air cooler, and real-time energy-consumption of pumps, fans and compressors. Performance index such as COP is calculated based on the practical

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operation results. The measurement instruments used are TESTO-480 handled multifunctional tester for the detection of air velocity, dry-bulb temperature and relative humidity (with sensitivity 0.01m/s, 0.01℃ and 0.1%RH), and FLUKE 365

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clamp meter, which was employed to the current and voltage measurement of electrical appliances (with sensitivity 0.1A and 0.1V). All instrumentations had been calibrated before measurement. The testing instruments are shown in Fig. 7 and onsite measurement situation is given in Fig. 8.

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Two experimental periods were arranged from July 27th to August 2nd, 2016 and from August 25th to August 31st, 2017, the hottest time in Beijing area according to the average day temperature [44]. Three test periods were carried out for each day in the morning (8:00~10:00), noon (12:00~14:00) and evening (17:00~19:00), respectively. The top cooling capacity of EC-AC system could be detected during the

Moring and evening are peak time, while noon is trough time.

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3.2 Measurement process

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test. The three testing periods are determined due to the cooling load change in a day.

According to the standard GB/T 14294-2008 [45], the equal area criterion was chosen to separate the cross section into 25 identical small rectangles. The dimension of

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evaporative condenser is 300mm*3200mm*4000mm (width*length*height). Testing

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points of the evaporative condenser were selected at 3.2m in front and 12.8m in

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behind. The measuring points were the diagonal intersection points of these rectangles

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as shown in Fig. 9. The data reading interval was 20s until reaching the steady state. Since there are two types of surface air coolers, the larger one is set in the air supply

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duct and the smaller one is installed in the air handling units, testing methods are designed differently. The measure method of the larger surface air cooler is same with

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the method of testing the evaporative condenser. The dimension of air cooler is 300mm*4400mm*5200mm (width*length*height). 25 testing points are set evenly.

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Subject to the limited space in the air handling units, the inlet cross section of the smaller surface air cooler is chosen between the draught fan and the cabinet door with five measure points to obtain the average value. In consideration of dispersive air

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outlets in the offices and equipment rooms, the state parameters of outlet cross section are measured by five random points and the average value is calculated. 3.3 Performance indces

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On basis of the first thermodynamic law, the system efficiency could be assessed by the Coefficient of Performance (COP). To distinct the difference of whole system, three kinds of COP values are calculated by the following equation. (1) COP of the cooling unit： COP = Qe ⁄Pc

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(1)

where 𝑄𝑒 (W) is the cooling capacity of the AC system, 𝑃𝑐 (W) is the instantaneous

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power of compressor. (2) COP of the cooling source：

(2)

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SCOP = Qe ⁄(Pc + PP + Pf )

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where Pp and Pf (W) are the instantaneous power of pump and fan.

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(3) COP of the EC-AC system：

(3)

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ACOP = Qe ⁄(Pc + PP + Pf + Ps + Ph )

where 𝑃𝑠 (W) and 𝑃ℎ (W) are the instantaneous power of supply and exhaust fan.

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In this measurement, the overall cooling capacity is approximately equal to the sum of total surface air coolers’ cooling capacity. 𝑄𝑒 is an indirect parameter that is obtained

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by equation (4) ：

𝑄𝑒 = 𝐺𝑠 (ℎ𝑠,𝑖𝑛 − ℎ𝑠,𝑜𝑢𝑡 )

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where Gs (kg/s) is the air mass flow rate through the surface air cooler, which is the product of air density, air velocity and cross section area. The enthalpy ℎ𝑠,𝑖𝑛 and ℎ𝑠,𝑜𝑢𝑡 (kJ/kg) could be looked up from psychrometric chart using the dry-bulb temperature and relative humidity of inlet and outlet.

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(4)

Error detection is achieved by equation system (5) to make sure that the calculated 𝑄𝑠 is able to accurately describe the cooling capacity of the system. If the deviation of |𝑄𝑠 + 𝑃𝑐 -𝑄𝑐 |and 𝑄𝑐 is less than 20% (Engineering allowance), the calculated 𝑄𝑠 is persuasive.

𝑄𝑐

≤ 20%

𝑄𝑐 = 𝐺𝑐 (ℎ𝑐,𝑖𝑛 − ℎ𝑐,𝑜𝑢𝑡 )

(5)

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|𝑄𝑠 +𝑃𝑐 −𝑄𝑐 |

(6)

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where 𝑄𝑐 (w) is the exchanged heat of the evaporative condenser and 𝐺𝑐 (kg/s) is the air mass flow rate of the cross section.

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𝑃𝑐 , 𝑃𝑝 and 𝑃𝑓 are reckoned using electrical current (I) and voltage (U):

(7)

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𝑃𝑖 = 𝑈𝑖 𝐼𝑖

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4. Discussion of testing results

The field testing was continuously conducted for one week, both in 2016 and 2017,

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while the measurement results on the morning of July 29th, 2016 and the morning of August 25th, 2017 are selected as typical working conditions. The first condition was

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operated in high efficiency compared to the average values, whereas the second condition was typically low efficiency. During the testing period, the air-handling

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units with small surface air cooler (part ③ in Fig 1) were shut down all the time because the returning air temperature was beneath the set temperature of the office where people worked.

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4.1 Analysis of high and low efficiency working conditions

Table 2 and Table 3 present the high efficiency working condition and low efficiency working condition of the EC-AC system in the Futong metro station. From the comparison of two working conditions, several conclusions could be obtained: 15

(1) The air temperature and humidity at the surface air cooler outlet are different. The designed model was operated as half cooling capacity in each side A/B. However, the result shows that neither the temperature, humidity nor the cooling capacity is equal in side A/B. The wet-bulb temperature of side A is nearly 1℃ higher than side B, the unbalance is probably caused by separated operation mode.

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(2) The balanced cooling capacity is inferred to be the pivotal parameter between the

high and low working conditions. Without consideration of climate and passengers of

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two working conditions, the most obvious difference is cooling capacity. The cooling

capacities of high efficiency working condition are 429/383kW of side A/B. Whereas, the cooling capacities of low-efficiency working condition are 531/270kW of side

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A/B. The COP of high efficiency working condition are 4.0/4.0 of side A/B. Whereas, the COP of low-efficiency working condition are 3.4/2.4 of side A/B. It could be seen

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that there is a big difference of cooling capacity between two working conditions.

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(3) The working performance is not stable as design operation model. In high efficiency working condition, it could be obtained that the average power

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consumption of compressor, water pump and fan are 101.7kW, 9.0kW and 17.4kW and the practical COP, SCOP and ACOP are calculated as 4.0, 3.2 and 2.1. In the low

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efficiency working condition, the average power consumption of compressor, water pump and fan are 134.3kW, 8.8kW and 2.2kW, leading to the total power

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consumption of the EC-AC system of 290.6kW. The practical COP, SCOP and ACOP are calculated as 2.9, 2.8 and 2.0. Our results indicate that the AC system consumes less electricity consumption totally in high-efficiency working condition. Hence ensuring the high efficiency working condition enables the EC-AC system to be

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highly energy-saving and effective.

4.2 Power consumption analysis 16

The comparison of high efficiency and low efficiency working condition is shown in Fig.10 and Fig.11. As observed from the testing results, the COP value of total average in the first condition is 4.0, exceeding the COP value of 3.0 for second condition by 33%. It is also observed that the compressors from low efficiency working condition consume more power of whole system in operation. Moreover, there is a big difference in power consumption of fan wall unit. In the low efficiency

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working condition, the fan wall power consumption is obviously declined, which would lead to an inadequate heat dissipation problem.

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In the low efficiency working condition, there is a significant difference of cooling capacity between side A (531 kW) and side B (270 kW), which is extremely

imbalanced compared to the high efficiency working condition. Discrepancy of

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cooling capacity is adopted to numerically reflect the unbalanced operation of two

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sides. We could assume that the difference of cooling capacity was caused by the

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inappropriate operation modes. If the modes were operated as designed condition, the

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cooling capacities of both sides would be similar.

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4.3 System performance over testing period

The numerical and statistical diagrams of the operating efficiency of each test

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condition are shown in Table 4 and Fig 12 (a, b, c) respectively. Through statistical data, the average refrigeration efficiency of COP, SCOP and ACOP in A and B side is up to 3.8/3.9, 3.4/3.4 and 2.5/2.3. As the rated condition COP is 4.3, the average level

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of the system efficiency both reaches the designing goal of the EC-AC system, observed from the data. Compared with COP values, the cooling source system efficiency SCOP decreases by 0.4/0.5, declined about 10%. Moreover, the air conditioning system efficiency ACOP decreases by 1.3/1.6, compared with SCOP, nearly 35%. This phenomenon explained 17

that the EC-AC system power consumption is mainly influenced by compressor, supply fan and exhaust fan. The power consumption of cooling source distribution including fan wall unit and water pump is far less than the centralized system. This is the advantage of EC-AC system design. From Fig. 12 it can be seen that the system efficiency does not change with the

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morning peak, noon and evening peak periods of passenger flow, presenting the "V" shape. The minimum/maximum COP of side A is 2.8/ 4.6; the minimum/maximum

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COP of side B is 2.4/ 4.6. The largest difference between two sides is 1.7.

The working efficiency of A and B side rarely matches up with each other. It should be figured out that the fundamental function and designed performance of the two

U

systems are almost the same. The actual operating status has great influence on the

M

A

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system performance.

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Fig. 12: System COP values of EC-AC system over testing period: COP value (a), SCOP value (b)

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and ACOP value (c)

Table 5 and Fig. 13 illustrate the total power consumption of EC-AC over testing period. This section respectively selected 9 working conditions points from 2016 and 2017 for analysis, in which the operating point 1-9 are from 2016 and 10-18 are from

A

2017. In order to investigate the relationship between passenger flow and power consumption, these 18 points are grouped by three testing time: 8:00 in the morning condition:1, 2, 5, 7, 10, 12, 13:00 condition: 3, 6, 8, 11, 13, 15, 17 and 17:00 condition: 4, 9, 14, 16, 18.

18

It can be seen from the Fig.13, the compressor consumes most energy consumption, the second is the main blower and the main exhaust fan, and evaporative condenser blower and circulating pump energy consumption accounted for the smallest proportion. This phenomenon reflects the characteristics of direct expansion system can consume less distribution power consumption.

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Table 6 and Fig.14 present the total cooling capacity of chiller of EC-AC systems over testing period. It is found out that the cooling capacity of chiller of side A is

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always higher than side B, with the average values 691kW against 400kW. On the one hand, it is shown that there is a great difference between designing cooling load and actual average cooling capacity (1940kW against 980kW). This phenomenon is

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attributed to that the cooling unit is chosen with excessive stock in cooling capacity. The cooling unit does not operate at the best working condition or even lies in the low

N

efficient working area. The total cooling capacity of side A ranges from 429kW to

A

902kW and the total cooling capacity of side B ranges from 327kW to 450kW. This

M

result indicates that most of cooling load is not handled by both systems equally but almost handled by side A. The long-time disequilibrium operation of two systems

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ED

may cause machine error and low efficiency.

A

Table 7 shows temperature data during testing period. From the table, it could be observed that concourse temperature is around 25.9℃, whereas platform temperature is around 25.3℃. Temperature inside the station is nearly 2℃ lower than outdoor temperature.

19

5. Economic and environmental benefits

A life-cycle analysis about the economic and environmental benefits of the EC-AC system in Beijing is carried out by using the mean performance values from above daily testing results. An established economic model is applied to evaluate the EC-AC system. This model includes three main indicators: payback-time prediction (PP), life-

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cycle net cost saving (CS) and life-cycle carbon emission (CR).

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5.1 Payback-time prediction

In order to prove the economic benefit of EC-AC system, a traditional WC-AC system is selected for compare purpose. The capital investments of two systems are

U

shown in Table 8. Aside from the saving in the investment of on-ground space, the

N

cost payback period for operating such EC-AC system in the metro station against the

𝑪𝒂𝒑𝒊𝒕𝒂𝒍 𝒄𝒐𝒔𝒕 𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒄𝒆

M

𝑷𝑷 =

A

conventional WC-AC system can be estimated by [46]

=

𝑪𝑬𝑪 −𝑪𝑾𝑪 𝑪𝒐,𝑾𝑪 −𝑪𝒐,𝑬𝑪

(8)

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𝑨𝒏𝒏𝒖𝒂𝒍 𝒐𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏 𝒄𝒐𝒔𝒕 𝒔𝒂𝒗𝒊𝒏𝒈

Before evaluating the economic benefits, annual power consumption of two systems are calculated. A typical WC-AC system with a COP value of 2.9 is adopted in Beijing.

PT

The COP 2.9 is referred from the measured data of a WC-AC system applied in the near metro station. Thus, under the same cooling capacity of EC-AC system, the

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average power consumption of WC-AC system in a day is 338kW. By considering the operation period of these two metro stations is from 5:30 to 23:30 (18 hours), June to September (four months), the annual electricity consumptions of two systems are

A

649058kWh and 730080kWh. It is obvious that there is a great amount of energy-saving of 81022kWh by using EC-AC system. The EC-AC system requires a much higher investment of nearly CNY 3,460,000 while the WC-AC only needs CNY 2,900,000 for the capital cost. The capital cost difference of two AC systems is about CNY 560,000. Electricity prices from State Grid are assumed at CNY 0.8/kWh in Beijing [47]. The 20

annual cost saving due to the operation of EC-AC system in the station is approximately CNY 64817.6. The EC-AC system’s payback period is therefore around 8.6 years in Beijing.

5.2 life-cycle net cost saving

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As an EC-AC system is usually considered to have a life span of 20 years in the metro system according to the officer of Beijing Urban Construction Design & Development

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Group CO , the life-cycle net cost saving of this AC system in energy bills can be determined by equation (22) at CNY 0.74 million.

U

𝑪𝑺 = (𝑳𝒊𝒇𝒆 𝒕𝒊𝒎𝒆 − 𝒑𝒂𝒚𝒃𝒂𝒄𝒌 𝒕𝒊𝒎𝒆) × 𝑨𝒏𝒏𝒖𝒂𝒍 𝒐𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏 𝒄𝒐𝒔𝒕 𝒔𝒂𝒗𝒊𝒏𝒈 （9）

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5.3 life-cycle carbon emission

A

Environmental benefits can be simply estimated by carbon emission. The CO2 emission

M

reduction is calculated by equation (23). The result is that EC-AC system is able to reduce about 1600tons carbon emission in Beijing depending on the electricity-to-CO2

ED

conversion factor (0.997 kg CO2/kWh in China [48]) throughout its life span of 20 years.

PT

𝑪𝑹 = 𝟎. 𝟗𝟗𝟕 × 𝑨𝒏𝒖𝒖𝒂𝒍 𝒑𝒐𝒘𝒆𝒓 𝒄𝒐𝒏𝒔𝒖𝒎𝒑𝒕𝒊𝒐𝒏 𝒔𝒂𝒗𝒊𝒏𝒈 × 𝑳𝒊𝒇𝒆 𝒕𝒊𝒎𝒆 (10)

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6. Conclusion

In this paper, a novel energy-efficient AC system incorporating an independent

A

evaporative condenser system is comprehensively investigated. The EC-AC system is installed at Futong metro station in Beijing, China. The EC-AC system overcomes some drawbacks of the tradition water cooling centralized air conditioning system, such as large space occupied, water leaking, cooling tower noise, considerable energy consumption and low system efficiency. Field measurements of the system in side A and side B are carried out in order to investigate the actual performance of EC-AC 21

system. In the testing program, several significant parameters including temperature, humidity, air velocity and other parameters were continually recorded for two weeks in 2016 and 2017. The main conclusions from the measurements are presented as followings. 

The most obvious phenomenon is the imbalanced cooling capacity of side A and

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side B between high and low efficiency working condition. In other words, the

compressor which contributes more cooling capacity works overloaded and

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leads to the low efficiency of the whole system. Similarly, the compressor which contributes less cooling capacity works insufficiently and also leads to the low efficiency of the whole system. According to the characteristic curve of system COP, this imbalance cooling capacity condition would cause decrease in system

The COP value of high efficiency working condition is 4.0, almost the same as

N



U

efficiency.

A

rated condition 4.3. This result illustrates that the operation mode influences the



M

system efficiency in EC-AC system.

During the testing period, the average refrigeration efficiency of COP, SCOP

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and ACOP in A and B side is up to 3.8/3.9, 3.4/3.4 and 2.5/2.3,as the rated condition COP is 4.3, the average efficiency levels of both systems reach the

PT

designing goal of the EC-AC system, observed from the data. Compared with COP values, the cooling source system efficiency SCOP decreased by 0.4/0.5,

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declined about 10% Moreover, the air conditioning system efficiency ACOP decreased by 1.3/1.6, compared with SCOP, nearly 35%.



Furthermore, an economic model is applied to analyze the application feasibility

A

and benefits of the EC-AC system against the conventional WC-AC system. The results show that energy saved by EC-AC system is up to 81022kWh annually with 11% decrease compared to WC-AC system. Despite of higher capital investment, the EC-AC system’s payback periods were around 8.6 years in Beijing and its life-cycle net cost saving in energy bills could be CNY 0.74 million. The corresponding CO2 emission reduction is estimated at 1600 tons 22

throughout the system’s life span of 20 years. The research results indicate that such EC-AC system is a feasible solution to enhance the energy efficiency and reduce the operational cost/carbon emission in the metro AC system. However, the EC-AC system is not operated in a designed condition nowadays. The real problem lies in that the EC-AC system is not operated designedly

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to increase system COP and optimize operating control strategies.

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and its control mode needs to be optimized. A nature extension of the current work is

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Acknowledgements

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The authors would acknowledge sincere appreciation to the financial supports from

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National Natural Science Foundation of China (Grant No. 51578011), National

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Natural Science Foundation of China (Major Program No. 51590912), National Natural Science Foundation of China (General Program No. 51378025), the IDIC

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(International Doctoral Innovation Centre) program of the University of Nottingham (China campus) and Beijing University of Technology Science and Innovation

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Service Capacity Building-Scientific Research Base-Beijing Laboratory-Urban

A

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Railway Transportation Beijing Laboratory(participate, municipal).

23

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[44]. http://www.weather.com.cn/weather/101010100.shtml

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[45]. Ministry of Construction, GB/T 14294-2008, Code for air handling units, China Planning Press, Beijing, 2008.

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[46]. Payback period, [August 12, 2016]. Available from: http://accountingexplained.com/managerial/capital-budgeting/payback-period

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[47]. Beijing electricity price, [August 24, 2016], Available from: < www.bjpc.gov.cn>.

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[48]. Electricity-to-CO2 conversion ratio, [August 26, 2016] Available from: < www.china5e.com>.

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Fig. 2: Schematic design of the EC-AC metro system

A

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ED

M

A

N

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Fig. 1: Schematic profile of a typical metro WC-AC system in China

28

IP T SC R

A

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PT

ED

M

A

N

U

Fig. 3: Evaporative condenser design of the EC-AC metro system

Fig. 4: Design of the EC-AC metro system in pilot project: side A

29

IP T SC R

A

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PT

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M

A

N

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Fig. 5: Design of the EC-AC metro system in pilot project: side B

Fig 6: Schematic profile of the EC-AC system in Futong station

30

A

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PT

ED

M

A

N

U

IP T

SC R

Fig. 7: TESTO-480 and FLUKE

31

IP T SC R U N A M ED PT CC E A Fig. 8: Onsite measurement pictures of the pilot project

32

IP T SC R U

M

A

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Fig. 9: Measuring points of the evaporative condenser and the surface cooler

Exhaust Fan Supply Fan Water Pump Fan Wall Compressor

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total

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2016/7/29 8:00

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B side

A

A side

0

50

100

150

200

250

300

350

400

Power Consumption(kW)

Fig. 10 High efficiency working condition

33

2017/8/25 8:00

total

Exhaust Fan Supply Fan Water Pump Fan Wall Compressor

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B side

A side

0

100

200

300

400

SC R

Power Consumption(kW)

A

N

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Fig. 11 Low efficiency working condition

4.5

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3.0

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COP

4.0

3.5

EC-AC Side A EC-AC Side B

M

5.0

2.5

0

2

4

6

8

10

12

14

Testing time 2016-2017

Fig. 12(a)

A

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2.0

34

16

18

20

EC-AC Side A EC-AC Side B

4.5

4.0

SCOP

3.5

3.0

2.0 0

2

4

6

8

10

12

14

16

18

20

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Testing time 2016-2017

N

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Fig. 12(b)

3.2

2.8

M

2.6 2.4 2.2

ED

ACOP

EC-AC Side A EC-AC Side B

A

3.0

2.0 1.8 1.6

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1.4

2

4

6

8

10

12

14

Testing time 2016-2017

Fig. 12(c)

A

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0

35

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2.5

16

18

20

18 16 14 9 4 17 15 13 11 8 6 3 12 10 7 5 2 1

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Exhaust Fan Supply Fan Water Pump Fan Wall Compressor

0

100

200

300

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time slot

2016/2017 Power Consumption Comparison

400

500

Power Consumption(kW)

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A

N

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Fig. 13: Total power consumptions of EC-AC system over testing period

2016/2017 Cooling Capacity Comparison

B side A side

A

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time slot

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18 16 14 9 4 17 15 13 11 8 6 3 12 10 7 5 2 1

0

200

400

600

800

1000

1200

Cooling Capacity(kW)

Fig. 14 Total cooling capacity of EC-AC system over testing period

36

Table 1: List of the main equipment in EC-AC system for the pilot project

Equipment

Amount

Property (size, capacity, power)

Cooling water pumps

2

48.7m³/h; 28m H2O; 5.5kW

Exhaust fan

1

216000m³/h; 1000Pa; 90kW

Supply fan

1

216000m³/h; 1000Pa; 90kW

Compressors

3

Cooling capacity of 800kW Rated power of 186kW 184000m3/h

Equipment

Amount

Property (size, capacity, power)

Cooling water pumps

2

48.7m³/h; 28m H2O; 5.5kW

Exhaust fan

1

216000m³/h; 1000Pa; 90kW

Supply fan

1

216000m³/h; 1000Pa; 90kW

Compressors

2

A

N

U

Side B

SC R

20

Fan wall

Cooling capacity of 800kW

138000m3/h

A

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PT

ED

15

M

Rated power of 186kW

Fan

37

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Side A

Table 2: 2016/7/29 8:00 high efficiency working condition

Testing objectives

Values

Temperature/humidity at surface air cooler inlet ℃/%

27.1/74.5

Enthalpy at surface air cooler inlet kJ/kg

70.5

Temperature/humidity at surface air cooler outlet ℃/%

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22.4/86.1

Enthalpy at surface air cooler outlet kJ/kg

60.2

Air flow rate of surface air cooler m³/h Cooling capacity Qs kW

SC R

125000 429.2

Temperature/humidity at evaporative condenser inlet ℃/% Enthalpy at evaporative condenser inlet kJ/kg

76.1

A

Air flow rate of evaporative condenser m³/h

Power of compressor kW

M

Heat exchanged, Qc kW Power of fan wall kW

N

Enthalpy at evaporative condenser outlet kJ/kg

U

Temperature/humidity evaporative condenser outlet ℃/% Side A

29.1/90.6 89 111000 477.3 21.8 107.7 9.0

ED

Power of cooling water pump kW

138.4

Error allowance %

13.8

PT

Total power kW

4.0

SCOP

3.1

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COP

ACOP

2.2

Temperature/humidity at surface air cooler inlet ℃/% Enthalpy at surface air cooler inlet kJ/kg

A

28.4/75.7

Temperature/humidity at surface air cooler outlet ℃/% Enthalpy at surface air cooler outlet kJ/kg

26.2/75.1 67.6 21.5/86.0 57.3

Side B Air flow rate of surface air cooler m³/h Cooling capacity Qs kW

111000 383.0

Temperature/humidity at evaporative condenser inlet ℃/% Enthalpy at evaporative condenser inlet kJ/kg 38

27.7/76.2 73.8

Temperature/humidity evaporative condenser outlet ℃/%

28.2/97.3

Enthalpy at evaporative condenser outlet kJ/kg

89.2

Air flow rate of evaporative condenser m³/h

81500

Heat exchanged, Qc kW

418.4

Power of fan wall kW

12.9

Power of compressor kW

95.78 9.0

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Power of cooling water pump kW

117.6

Error allowance %

15.8

COP

4.0

SC R

Total power kW

SCOP

3.3

ACOP

2.1

Cooling capacity Qs kW

812

U

Power of fan wall kW

N

Power of compressor kW Power of cooling water pump kW

A

Total Average COP Average SCOP

M

Total power kW

203.5 18.0 256.3 4.0 3.2 2.1

A

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PT

ED

Average ACOP

34.7

39

Table 3: 2017/8/25 8:00 low efficiency working condition Testing objectives

Values

Temperature/humidity at surface air cooler inlet ℃/%

25.7/55.1

Enthalpy at surface air cooler inlet kJ/kg

54.8

Temperature/humidity at surface air cooler outlet ℃/%

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14.8/91.8

Enthalpy at surface air cooler outlet kJ/kg

39.2

Air flow rate of surface air cooler m³/h

102138

Cooling capacity Qs kW

SC R

531

Temperature/humidity at evaporative condenser inlet ℃/% Enthalpy at evaporative condenser inlet kJ/kg

47.8

Enthalpy at evaporative condenser outlet kJ/kg

A

Heat exchanged, Qc kW

M

Power of fan wall kW Power of compressor kW

N

Air flow rate of evaporative condenser m³/h

U

Temperature/humidity evaporative condenser outlet ℃/% Side A

ED

Power of cooling water pump kW

83.4 52355 621 2.5 154.3 9.0 138.4

Error allowance %

-10.4

PT

3.4 3.3

ACOP

2.4

CC E

SCOP

Temperature/humidity at surface air cooler inlet ℃/% Enthalpy at surface air cooler inlet kJ/kg Temperature/humidity at surface air cooler outlet ℃/%

A

27.8/91.6

Total power kW

COP

Side B

26.6/38.2

Enthalpy at surface air cooler outlet kJ/kg Air flow rate of surface air cooler m³/h Cooling capacity Qs kW

24.3/49.4 48.2 17.4/77.9 41.9 128427 270.0

Temperature/humidity at evaporative condenser inlet ℃/% Enthalpy at evaporative condenser inlet kJ/kg

40

28.3/26.3 44.5

Temperature/humidity evaporative condenser outlet ℃/%

29.6/92.2

Enthalpy at evaporative condenser outlet kJ/kg

92.1

Air flow rate of evaporative condenser m³/h

26212

Heat exchanged, Qc kW

416

Power of fan wall kW

1.9

Power of compressor kW

114.3

Power of cooling water pump kW

8.6 117.6

IP T

Total power kW

7.6

COP

2.4

SC R

Error allowance %

SCOP

2.2

ACOP

1.5

Cooling capacity Qs kW

801

U

Power of fan wall kW

N

Power of compressor kW Power of cooling water pump kW

A

Total Average COP Average SCOP

M

Total power kW

268.6 13.1 286.1 3.0 2.8 2.0

A

CC E

PT

ED

Average ACOP

4.4

41

Table 4: System COP values of EC-AC system over testing period

ED PT CC E A

42

B/ACOP 2.6 2.1 2.3 2.1 2.1 2.4 1.8 2.0 2.2 1.5 1.5 2.4 2.4 2.5 2.9 2.7 2.7 2.5 2.3

IP T

A/ACOP 2.4 2.2 2.3 2.3 2.8 3.0 2.5 2.6 2.7 2.4 2.8 2.5 1.9 2.6 3.0 3.0 2.3 2.3 2.5

SC R

B/SCOP 4.0 3.2 3.7 3.3 3.4 3.8 3.0 3.3 3.5 2.2 2.2 3.7 3.6 3.7 4.2 3.8 3.8 3.6 3.4

U

A/SCOP 2.9 3.1 2.8 2.8 3.8 3.8 3.3 3.4 3.6 3.3 3.8 3.4 2.6 3.6 4.2 4.2 3.2 3.1 3.4

N

B/COP 4.4 4.0 4.5 4.0 4.0 4.5 3.6 3.8 4.1 2.4 2.4 4.0 4.0 4.1 4.6 4.1 4.1 3.9 3.9

A

A/COP 3.5 4.0 3.2 3.2 4.6 4.3 4.0 4.1 4.2 3.4 4.1 3.7 2.8 3.9 4.5 4.5 3.4 3.4 3.8

M

Condition 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 average

Table 5: Total power consumptions of EC-AC system over testing period

ED PT CC E A

43

Total/k W 519 384 516 530 403 474 435

IP T

Exhaustfan/kW 60 61 61 61 62 62 67 67 63 55 55 55 55 55 55 55 55 55

SC R

Supplyfan/kW 66 66 66 66 65 65 66 66 67 64 64 64 64 64 64 64 64 64

U

Waterpump/kW 18 18 18 18 19 19 19 19 19 13 18 18 18 18 17 17 17 17

N

Fanwall/kW 36 35 35 34 27 27 31 31 30 4 4 4 4 4 4 4 4 4

A

Compressor /kw 339 203 336 350 231 302 252 263 260 269 266 252 259 254 263 271 275 269

M

Conditi on 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

446 439 404 407 393 399 394 403 411 416 410

Table 6: Total cooling capacity of EC-AC system over testing period

M ED PT CC E A

44

Total(kW)

IP T

1289 810 1192 1192 1017 1318 967 1044 1087 801 892 963 848 1012 1196 1179 1028 977

SC R

B/Cooling Capacity(kW) 510 381 429 396 363 418 329 381 403 270 264 438 446 457 557 536 538 496

U

2016/7/28 8:00 2016/7/29 8:00 2016/7/29 13:00 2016/7/29 17:00 2016/7/30 8:00 2016/7/30 13:00 2016/7/31 8:00 2016/7/31 13:00 2016/7/31 17:00 2017/8/25 8:00 2017/8/25 13:00 2017/8/26 8:00 2017/8/26 13:00 2017/8/26 17:00 2017/8/30 13:00 2017/8/30 17:00 2017/8/31 13:00 2017/8/31 17:00

A/Cooling Capacity(kW) 779 429 763 796 654 900 638 663 683 531 628 525 402 555 639 643 490 481

A

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Testing Time

N

Condition

Table7 Station Temperature

Outdoor Temperature/℃

Concourse Temperature/℃

Platform Temperature/℃

1

28.3

27.1

26.4

2

28.2

25.5

25.3

3

31.2

26.3

25.9

4

31.6

25.4

5

28.1

26.5

6

30.2

26.1

7

26.8

25.2

8

27.3

25.5

9

27.5

24.6

10

27.4

26.5

11

28.5

26.7

12

26.1

25.4

13

26.9

14

25.9

15

26

16

25.8

17

26

18

25.3 25.7

SC R

25.6 24.9 25.1 25

N

U

25.6 26

25.6 24.7

26.3

25.6

26.5

24.1

25.3

24

25.9

24.9

26

25.6

25

27.7

25.9

25.3

ED

M

A

25.8

A

CC E

PT

Average

IP T

Condition

45

Table 8: Estimation of capital investment of two different AC systems Evaporative condenser air conditioning (EC-AC) system Amount

Cost (‘000CNY)

Evaporative condenser

2

1000

Compressor

7

1000

Large-scale direct-expansion surface air cooler

2

1000

Direct-expansion combined air conditioning box

3

150

Circulating water pumps

2

10

Refrigerator room group control

1

100

Refrigerant pipe system

---

200

Total

---

3,460

U

SC R

IP T

Components

Water-cooling air conditioning (WC-AC) System Amount

Cost (‘000CNY)

3

1500

3

350

2

460

3

80

Chilled /cooling water pump

6

60

Refrigerator room group control system

1

100

Chilled/cooling water loop, the device of stabilizing pressure and making up water, Water treatment equipment, water system damper Sub-water Catcher etc.

---

350

Total

---

2,900

N

Components

A

Water-cooled chiller

Large-scale surface air cooler

A

CC E

PT

ED

The combined air conditioning box

M

Cooling tower

46