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Pressure drop study on an Organic Rankine System utilizing LNG cryogenic energy and waste heat recovery
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Energy (2019) 000–000 718–725 EnergyProcedia Procedia158 00 (2017) www.elsevier.com/locate/procedia
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Pressure drop study on an Organic Rankine System utilizing LNG The 15th International Symposium Rankine on District Heating and utilizing Cooling Pressure drop study on an Organic System LNG cryogenic energy and waste heat recovery cryogenic energy and waste heat recovery Assessing the feasibility of using the heat demand-outdoor Yi Liaa*, Dawei Wuaa,Ben Wetenhallaa Yi Li Wu ,Bendistrict Wetenhallheat demand forecast temperature function for*, aDawei long-term School of Engineering, Newcastle University, Armstrong Building, Newcastle upon Tyne, NE1 7RU, United Kingdom
a
a,b,c a b c of Engineering, Armstrong Newcastle Tyne, NE1 7RU,, United Kingdom I. School Andrić *, A.Newcastle Pinaa,University, P. Ferrão , J. Building, Fournier ., B.uponLacarrière O. Le Correc a
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract Liquid natural gas (LNG) occupies an important place in global energy market. In 2015, gas occupied 45% of global energy Liquid natural (LNG)demand occupiesforanfuel important placegeneration in global [1]. energy 2015, occupied 45% of energy demand driven by gas increases and power Themarket. outlookInfor LNGgas usage is positive andglobal continues to demand driven by increases demand for fuel and power generation [1]. The outlook for LNG usage is positive and continues to gain momentum [2]. Abstract gain momentum [2]. the pressure drop in an Organic Rankine Cycle (ORC) system used to recover energy from an LNG engine This paper studies Thisapaper studies Organicresearch Rankineand Cycle (ORC) system used to recover energy fromutilization. an LNG engine aboard ship and aimsthe to pressure fill in thedrop gapsinofan previous provide more details of LNG cryogenic energy Districta ship heating addressedresearch in the literature as more one of the most effective solutions decreasing the aboard and networks aims fillare in commonly the gaps of previous and provide details of LNG cryogenic energyfor utilization. The ORC utilizes thetotemperature difference between the exhaust gas and LNG to generate power. The thermodynamic process greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat The ORCusing utilizes the temperature difference between is modelled an Engineering Equation Solver (EES).the exhaust gas and LNG to generate power. The thermodynamic process sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, is modelled using anofEngineering Solver The calculation the pressureEquation drop starts with(EES). the heat exchangers in the cycle which are modelled as plate heat exchangers prolonging the investment return period. of the pressure drop The startseffect with of thethe heat exchangers which are modelled plate heat exchangers for The bothcalculation the evaporator and condenser. pressure dropsininthe thecycle heat exchangers on wholeassystem is then studied. The main of this and paper is to assess theeffect feasibility ofpressure using the heatindemand temperature function is forthen heatstudied. demand for both thescope condenser. The of thedecreases drops theefficiency heat– outdoor exchangers on whole The results ofevaporator the calculation are that the pressure drop the system and increases withsystem the fluids’ mass flow forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted 665 The results of the calculation the pressure drop decreases the system efficiency and increases with the fluids’ massofflow rate. The difference between are the that working temperature range of fluids and actual working temperature range will increase the buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district rate. Theinfluence difference the drops. working temperature range of fluids and actual working temperature range will increase the negative of between the pressure renovation scenarios were developed negative influence of the pressure drops.(shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. Copyright © 2018 Elsevier Ltd. All rights reserved. ©The 2019 The Authors. Published by Elsevier Ltd. results that when weather change is considered, the margin of error could be acceptable for some applications Copyright © showed 2018 Elsevier Ltd. only All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy This iserror an open accessdemand article under the CCthan BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) (the in annual was lower 20% for all weather scenarios considered). However, after introducing renovation th International Selection and peer-review under responsibility of the scientific committee of the 10 Conference onApplied Applied Energy (ICAE2018). Peer-review under responsibility of theupscientific committee of ICAE2018 – Theand 10threnovation International Conference on Energy. scenarios, the error value increased to 59.5% (depending on the weather scenarios combination considered). (ICAE2018). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: Organic Rankine cycle; heat exchanger; pressure drop decrease Organic in the number heating hours of pressure 22-139hdrop during the heating season (depending on the combination of weather and Keywords: Rankine of cycle; heat exchanger; renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +44(0)7563325654
address:author. [email protected] * E-mail Corresponding Tel.: +44(0)7563325654 Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.193
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1. Introduction As a cleaner burning gas, LNG is already the fuel of choice for part of transportation area. For transportation systems, LNG needs to be vaporized to a gaseous state before it enters the main engine. The exhaust gas from the engine and the latent energy from the vaporization process have a large amount of potential energy to utilize. In previous research, an ORC system has been built for dual reutilization of LNG latent energy and thermal waste energy in marine applications [3]. However, the pressure drop which occurs in the cycle has not yet been fully investigated. Lei et al [4] tried to make clear which kind of pressure losses can affect the system efficiency. They classified the losses into three categories of pressure losses in the cycle and found that the LPL (low pressure losses) are mainly responsible for efficiency decrease [4]. In this study, the model for the ORC system follows the structure of previous research and focuses on the pressure drop with different working fluids and the relationship of the working fluid to the performance of the cycle. To simplify the calculations, a few simplifications are made: The isotropic efficiency of the pumps and expanders are assumed to be constant values of 0.6 and 0.7 respectively. The mechanical efficiency of pumps and expanders is assumed to be 0.9. The turbines and pumps in the simulation are in 100% load conditions. The working fluid in the ORC will expand from the highest limited pressure to atmospheric pressure, which is 15bar to 1bar [3]. According to the actual LNG gas storage system [5], LNG will be evaporated from 5 bar 135℃ to 15 bar, then it will be expanded back to 5 bar. 2. Modelling and ORC system structure 2.1. ORC system with direct expansion of LNG The ORC system consists of two parts in this paper, which is shown in Fig. 1. The main cycle is a basic organic Rankine cycle. The pump is used to drive the working fluid and add its pressure from atmospheric pressure to 15 bar. A single turbine is in the cycle to use the evaporated working liquid to generate the power. The other part of the system is a direct expansion process of LNG, which is driven to go through the cold side of the condenser in the main cycle and acts as the heat sink for the main cycle and outputs PV work by another expander.
Fig. 1. Schematic of ORC system combined direct expansion of LNG There are three phase-changing stages, which occur in the evaporating side of the evaporator and the condensing and cooling sides of the condenser. It is noted that two-phase flow can cause a higher pressure drop because of the different flow rates of gas-phase flow and liquid-phase flow.
Yi Li et al. / Energy Procedia 158 (2019) 718–725 Author name / Energy Procedia 00 (2018) 000–000
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(a)
3
(b)
Fig. 2. (a) Main ORC thermodynamic cycle with Ethylene; (b) The direct expansion process with LNG (CH4) From the Fig. 2, there are three phase-changing stage, which occur in the evaporating side of evaporator, both condensing side and cooling side of condenser. Because of the friction between the surface of liquid and vapor, there will be a higher pressure drop happened in the heat exchanger than the single phase one. 2.2. System efficiency and design In the theoretical analysis, the pressure drop in cycle is always related to the thermal efficiency, according to the efficiency equation: 𝜂𝜂𝑂𝑂𝑂𝑂𝑂𝑂 =
𝑊𝑊𝑜𝑜𝑜𝑜𝑜𝑜 −𝑊𝑊𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝
(1)
𝑄𝑄𝑖𝑖𝑖𝑖,𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡
which is used to calculate the system efficiency of ORCs. From the equation (2), it is obvious to see that if the pressure drop increases, the work done by the pump increases and the output work from the turbine decreases. This is because of the lower pressure ratio. This view is supported by Lei et al, who provided a detailed correlation to relate the thermal efficiency to the pressure [4], which is: 𝑑𝑑𝑑𝑑𝑂𝑂𝑂𝑂𝑂𝑂 = −
𝜂𝜂𝑡𝑡 𝑇𝑇1′𝑠𝑠
𝑞𝑞1 𝑇𝑇1′
𝑣𝑣1′ 𝑑𝑑Δ𝑃𝑃𝐻𝐻1 −
𝑣𝑣3
𝑞𝑞1 𝜂𝜂𝑝𝑝
𝑑𝑑Δ𝑃𝑃𝐻𝐻2 −
𝜂𝜂𝑡𝑡
𝑞𝑞1
𝑣𝑣1′𝑠𝑠 𝑑𝑑Δ𝑃𝑃𝐿𝐿
(2)
where ηt and ηp are the isentropic efficiency of the expander and pump. vi is the specific volume, q1 is the heat absorbed by working fluids in cycle and ΔPH1, ΔPH2 and ΔPL refer to the pressure drops occurring in the two-phase stages of the evaporator and the preheating stages in the evaporator and in the condenser. In this study, the evaporator and condenser are both plate heat exchangers (PHE). The design method of the PHEs in this paper is the logarithmic mean temperature difference (LMTD) method. A countercurrent flow model is selected for the PHEs, then the logarithmic mean temperature difference can be calculated using: Δ𝑇𝑇𝐿𝐿𝐿𝐿 =
(𝑇𝑇1 −𝑡𝑡2 )−(𝑇𝑇2 −𝑡𝑡1 ) 𝑇𝑇2 −𝑡𝑡1
and heat transfer coefficient can be calculated using: 1
h
=
1
ℎℎ
+
(3)
𝑇𝑇 −𝑡𝑡 𝐼𝐼𝐼𝐼 1 2
1
ℎ𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐
𝛿𝛿
+ + 𝐾𝐾
1
ℎ𝑐𝑐
+
1
ℎ𝑒𝑒𝑒𝑒𝑒𝑒
The subscripts ‘h’ and ’c’ mean the single-phase stage for the hot and cold side respectively. The overall heat transfer area is then obtained as:
(4)
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A=
721
Q
(5)
∆𝑇𝑇𝐿𝐿𝐿𝐿 ℎ
To check the accuracy of the results, the calculation is checked against the number of plates (np), (6) (7)
𝑛𝑛𝑝𝑝 = 𝑛𝑛ℎ + 𝑛𝑛𝑐𝑐 + 1 𝑛𝑛𝑝𝑝 𝐴𝐴𝑝𝑝 = 𝐴𝐴
where nh and nc are the number of flow pass in the PHE. The whole design process is repeated to determine the number of flow passes and heat transfer under certain heat transfer load and geometric parameters. Fig. 3 shows the entire process and assumed parameters. The overall heat transfer calculation is divided into several parts, which are the single phase stage, the two phase stage and the heat resistance of the plates. The correlations used for the overall heat transfer calculation are listed in Table 1. Table 1 Correlation for the calculation of heat transfer Stage of heat transfer Single-phase convection stage
Correlation h=
Condensation stage
𝑁𝑁𝑁𝑁×𝑘𝑘 𝐷𝐷𝑒𝑒
h𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 =
Evaporation stage
=
1
0.205𝑃𝑃𝑃𝑃 3(𝑓𝑓×𝑅𝑅𝑅𝑅 2 𝑠𝑠𝑠𝑠𝑠𝑠2𝛽𝛽)0.374 ×𝑘𝑘
𝑁𝑁𝑁𝑁×𝑘𝑘 𝐷𝐷𝑒𝑒
h′ =
=
𝐷𝐷𝑒𝑒 0.3𝑅𝑅𝑅𝑅𝑒𝑒𝑒𝑒 0.7 𝑃𝑃𝑟𝑟 0.33 (𝜇𝜇/𝜇𝜇𝑤𝑤 )×𝑘𝑘
𝐷𝐷𝑒𝑒 𝑅𝑅𝑅𝑅∙Pr(𝑓𝑓/2)(𝑘𝑘/𝐷𝐷𝑒𝑒 )
[6] [7]
2
1.07+12.7(𝑃𝑃𝑃𝑃 3 −1)(𝑓𝑓/2)0.5
h = (1.136𝐶𝐶𝐶𝐶 −0.9 + 66702𝐵𝐵𝐵𝐵 0.7 ∗ 𝐹𝐹𝑓𝑓1 )ℎ′[8]
where Reeq is the equivalent Reynold number. Co and Bo are the convection number and nucleate number respectively. The ORC utilizes the temperature difference between the exhaust gas and LNG to generate power. The thermodynamic process is modelled using an Engineering Equation Solver (EES). Three different working fluids for the cycle are tested to ascertain their influence on the pressure drop. To simplify the calculations, the isotropic efficiency for the pump and expanders are assumed to be 0.6 and 0.7 respectively and the mechanical efficiency is assumed to be 0.9 for both. The properties of the fluids are obtained from the EES and NIST’s database
, the geometric and thermal parameters are used to evaluate the pressure drop in it. Generally, the categories of pressure drop (∆P) in the PHE can be classified into four kinds: flow pressure drop, elevation pressure drop, momentum pressure drop and port pressure drop. Port pressure drop can be calculated by ∆𝑃𝑃𝑃𝑃 =
1.5𝐺𝐺𝑝𝑝 2 𝑛𝑛𝑝𝑝
(8)
2𝜌𝜌
The most common method of calculating flow pressure drop of single phase flow in PHEs is the Darcy-Weisbach equation. Δ𝑃𝑃 = 4𝑓𝑓
𝐿𝐿 𝜌𝜌𝑤𝑤2
𝐷𝐷𝑒𝑒
(9)
2
However, for two-phase flow, the Darcy equation cannot be used directly and the Lockhart-Martinelli (L-M) method has to be used to obtain the frictional pressure loss using a correction factor found by relation equations with the Martinelli factor [10]. ∆𝑃𝑃𝑓𝑓 = 4𝑓𝑓
𝐿𝐿 𝐺𝐺 2
𝐷𝐷𝑒𝑒 2𝜌𝜌
𝜑𝜑 2
Here φ2 is two-phase friction multiplier which can compute the single-phase flow pressure drop both vapor and liquid phase:
(10)
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𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑
5
𝑑𝑑𝑑𝑑
( )𝑓𝑓𝑓𝑓,𝑡𝑡𝑡𝑡 = ( )𝑓𝑓𝑓𝑓,𝑙𝑙 𝜑𝜑𝑙𝑙 2 = ( )𝑓𝑓𝑓𝑓,𝑔𝑔 𝜑𝜑𝑔𝑔 2 𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑
and is a function of X, the Martinelli parameter. X is defined as follows:
𝑋𝑋 2 =
The relations between φ2 and X are:
(11)
𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑 ) 𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓 𝑑𝑑𝑑𝑑 ( ) 𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓
(
(12)
(13) (14)
𝜑𝜑𝑔𝑔 2 = 1 + 𝑐𝑐𝑐𝑐 + 𝑋𝑋 2 𝑐𝑐
2
φ𝑙𝑙 = 1 + + 𝑋𝑋
1
𝑋𝑋 2
where the constant c is determined by the flow conditions [9], as shown in Table 2. Table 2. Comparison table for constant c and flow conditions Constant c Flow condition c=20 For liquid and vapor both turbulent c=12 For liquid-laminar, vapor-turbulent c=10 For liquid-laminar, vapor-laminar c=5 For liquid and vapor both laminar Zhong-zheng Wang and Zhen-Nan Zhao [10] showed the correlations for calculating the momentum and elevation pressure drops are ∆𝑃𝑃𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = 𝐺𝐺 2 {[
(1−𝑥𝑥2 )2
𝜌𝜌𝑙𝑙 (1−𝜑𝜑2 )
−
𝑥𝑥2 2
𝜌𝜌𝑣𝑣 𝜑𝜑2
]−[
(1−𝑥𝑥1 2 )
𝜌𝜌𝑙𝑙 (1−𝜑𝜑2 )
−
𝑥𝑥1 2
𝜌𝜌𝑣𝑣 𝜑𝜑2
∆𝑃𝑃𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 = 𝑔𝑔𝑔𝑔[𝜌𝜌𝑣𝑣 𝜑𝜑 + 𝜌𝜌𝑙𝑙 (1 − 𝜑𝜑)] The total pressure drop is obtained by summing Equation (8), (9), (15) and (16).
(15)
]}
(16)
2.3. Selection of working fluids Along with the geometric parameters of the PHE, the kind of working fluid also can affect the pressure drop in the PHE. Working fluids are operated from about their boiling point under atmospheric pressure to 200 oC. To take full advantage of the cryogenic energy of LNG, the fluids’ freezing point and boiling point are the key factors in selecting the working fluid. As in the previous research [3], the fluids are selected. These fluids and their properties are listed in Table 3 Table 3. Working fluids properties Freezing Point (oC) Ethylene C2H4 Propylene Isobutane R600a
-169 -185 -160
Boiling point (oC) -103.9 -47.78 -11.78
Critical Temperature (˚C) 9.2 91.7 134.7
Critical Pressure (bar) 50.42 46.65 36.4
Molar mass (g/mol) 28.05 42.08 58.12
3. Result and discussion Now that a simulation model has been established, the pressure drop in PHE can be evaluated. The three working fluids shown in Table 3 were tested in the condenser and the evaporator model described above. The mass flow rate increases from 0.004kg/s to 0.04kg/s.
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Fig. 3(a) (b) shows the working fluid’s and methane’s pressure drop in the model against the mass flow rate of working fluids. From the figure, it is clear that pressure drop is related to the mass flow rate with Propylene showing the highest pressure drop in both sides of the condenser and in the evaporator. To validate the prediction, Other researchers' predictions in plate heat exchangers will be cited here to compare the predicted value. The similar magnitude of the values shows that the prediction in this paper is persuasive. The cited researches are listed in Table 4 Table 4. Recent researches in PHE of two-phase flow’s pressure drop Author Working Fluid DongChan et al (2018)[11] R-1233zd(E) Amalfi et al (2016)[12] R245fa Vakili-Farahani et al (2014)[12] R245fa Kitti and Somchai (2010)[13] Air-water
Pressure Drop (kPa) 2~28 4~25 6~23 8~70
Fig. 4(a) (b) show the influence of pressure drops caused by different mass flow rate with different working fluids on systems’ efficiency.
PRESSURE DROP (KPA)
Ethlyene 40 35 30 25 20 15 10 5 0
4
8
12
Propylene
16
20
24
R600a
28
32
36
40
MASS FLOW RATE (G/S)
(a) Ethlyene
Propylene
R600a
PRESSURE DROP (KPA)
12 10 8 6 4 2 0
4
8
12
16
20
24
28
32
36
40
MASS FLOW RATE (G/S)
(b) Fig. 3. (a) Pressure drop of working fluids in model (b) Pressure drop of methane in simulation
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Ethlyene
Propylene
R600a
18 16
EFFICIENCY(%)
14 12 10 8 6 4 2 0
4
8
12
16
20
24
28
32
36
40
36
40
MASS FLOW RATE (G/S)
(a) Ethylene
Propylene
R600a
25.39 25.38 EFFICIENCY（%）
25.37 25.36 25.35 25.34 25.33 25.32 25.31 25.3
4
8
12
16
20
24
28
32
MASS FLOW RATE (G/S)
(b) Fig.4. (a) ORC’s efficiency (b) Expansion efficiency of LNG As shown in Fig 4, the maximum simulation efficiency is 15.57% in the ORC system and 25.4% in LNG’s expansion. The efficiency for both the ORC and direct expansion decrease as pressure drop increases. Ethylene, is shown to be the most suitable working fluid as it achieves the highest efficiency over the range of mass flow rates (from 15.53% to 14.46%). The Propylene achieves efficiencies ranging from 12.33% to 10.23%. R600a has the lowest system efficiencies ranging from 10.1% to 8.4%. It is noted that the pressure drops caused by Ethylene and R600a are similar. However, Ethylene has a better working temperature range. The decrease in efficiency over the full range of mass flow rates for LNG expansion is similar for each working fluid, around 0.1%. The lowest value is obtained by Propylene, which is 25.33%
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4. Conclusions According Equations (1) & (2), pressure drops have a negative impact on the performance of ORC systems. This paper introduces a way to evaluate pressure drop inside a PHE and analyze its influence on system efficiency. The conclusions of the study are: Pressure drop increases with mass flow rate. Propylene shows the greatest drop in efficiency over the total range of mass flow rates. The efficiency of direct expansion decreases as the pressure drop increases. Ethylene and R600a show similar pressure drops but R600a shows the greatest drop in efficiency over the range of mass flow rates. This is due to the temperature range of the fluids. References [1] Shell (2017) shell-lng-outlook2017-slides-master-march2017. Shell. Available at: (Accessed: 15 December 2017). [2] IGU-World LNG Report-2015 Edition (2015) International gas union. Available at: (Accessed: 15 December 2017). [3] Tsougranis, E. and Wu, D. (2017) Dual Reutilization of LNG Cryogenic Energy and Thermal Waste Energy with Organic Rankine Cycle in Marine Applications. Energy Procedia, 142, pp. 1401-1406. [4] Lei, B., Wu, Y., Ma, C., Wang, W., and Zhi, R. (2017) Theoretical analyses of pressure losses in organic Rankine cycles. Energy Conversion and Management, 153, pp. 157-162. [5] Wärtsilä Ship Power (2013) Gas Storage and supply systems. Available at: (Accessed: 10 May 2018). [6] Martin, H. (1996) A theoretical approach to predict the performance of chevron-type plate heat exchangers. Chemical Engineering and Processing: Process Intensification, 35(4), pp. 301-310. [7] Kumar, H. (1983) CONDENSATION DUTIES IN PLATE HEAT EXCHANGERS. Institution of Chemical Engineers Symposium Series, 75, PP. 478-509 [8] Kandlikar, S. (1991) Development of a Flow Boiling Map for Subcooled and Saturated Flow Boiling of Different Fluids Inside Circular Tubes. Journal of Heat Transfer, 113(1), p. 190. [9] Chisholm, D. (1967) A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow. International Journal of Heat and Mass Transfer, 10(12), pp. 1767-1778. [10] WANG, Z. and ZHAO, Z. (1993) Analysis of Performance of Steam Condensation Heat Transfer and Pressure Drop in Plate Condensers. Heat Transfer Engineering, 14(4), pp. 32-41. [11] Lee, D., Kim, D., Park, S., Lim, J. and Kim, Y. (2018). Evaporation heat transfer coefficient and pressure drop of R-1233zd(E) in a brazed plate heat exchanger. Applied Thermal Engineering, 130, pp.1147-1155. [12] Grabenstein, V., Polzin, A., and Kabelac, S. (2017) Experimental investigation of the flow pattern, pressure drop and void fraction of two-phase flow in the corrugated gap of a plate heat exchanger. International Journal of Multiphase Flow, 91, pp. 155-169. [13] Nilpueng, K. and Wongwises, S. (2010) Two-phase gas–liquid flow characteristics inside a plate heat exchanger. Experimental Thermal and Fluid Science, 34(8), pp. 1217-1229.
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10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Pressure drop study on an Organic Rankine System utilizing LNG The 15th International Symposium Rankine on District Heating and utilizing Cooling Pressure drop study on an Organic System LNG cryogenic energy and waste heat recovery cryogenic energy and waste heat recovery Assessing the feasibility of using the heat demand-outdoor Yi Liaa*, Dawei Wuaa,Ben Wetenhallaa Yi Li Wu ,Bendistrict Wetenhallheat demand forecast temperature function for*, aDawei long-term School of Engineering, Newcastle University, Armstrong Building, Newcastle upon Tyne, NE1 7RU, United Kingdom
a
a,b,c a b c of Engineering, Armstrong Newcastle Tyne, NE1 7RU,, United Kingdom I. School Andrić *, A.Newcastle Pinaa,University, P. Ferrão , J. Building, Fournier ., B.uponLacarrière O. Le Correc a
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract Liquid natural gas (LNG) occupies an important place in global energy market. In 2015, gas occupied 45% of global energy Liquid natural (LNG)demand occupiesforanfuel important placegeneration in global [1]. energy 2015, occupied 45% of energy demand driven by gas increases and power Themarket. outlookInfor LNGgas usage is positive andglobal continues to demand driven by increases demand for fuel and power generation [1]. The outlook for LNG usage is positive and continues to gain momentum [2]. Abstract gain momentum [2]. the pressure drop in an Organic Rankine Cycle (ORC) system used to recover energy from an LNG engine This paper studies Thisapaper studies Organicresearch Rankineand Cycle (ORC) system used to recover energy fromutilization. an LNG engine aboard ship and aimsthe to pressure fill in thedrop gapsinofan previous provide more details of LNG cryogenic energy Districta ship heating addressedresearch in the literature as more one of the most effective solutions decreasing the aboard and networks aims fillare in commonly the gaps of previous and provide details of LNG cryogenic energyfor utilization. The ORC utilizes thetotemperature difference between the exhaust gas and LNG to generate power. The thermodynamic process greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat The ORCusing utilizes the temperature difference between is modelled an Engineering Equation Solver (EES).the exhaust gas and LNG to generate power. The thermodynamic process sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, is modelled using anofEngineering Solver The calculation the pressureEquation drop starts with(EES). the heat exchangers in the cycle which are modelled as plate heat exchangers prolonging the investment return period. of the pressure drop The startseffect with of thethe heat exchangers which are modelled plate heat exchangers for The bothcalculation the evaporator and condenser. pressure dropsininthe thecycle heat exchangers on wholeassystem is then studied. The main of this and paper is to assess theeffect feasibility ofpressure using the heatindemand temperature function is forthen heatstudied. demand for both thescope condenser. The of thedecreases drops theefficiency heat– outdoor exchangers on whole The results ofevaporator the calculation are that the pressure drop the system and increases withsystem the fluids’ mass flow forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted 665 The results of the calculation the pressure drop decreases the system efficiency and increases with the fluids’ massofflow rate. The difference between are the that working temperature range of fluids and actual working temperature range will increase the buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district rate. Theinfluence difference the drops. working temperature range of fluids and actual working temperature range will increase the negative of between the pressure renovation scenarios were developed negative influence of the pressure drops.(shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. Copyright © 2018 Elsevier Ltd. All rights reserved. ©The 2019 The Authors. Published by Elsevier Ltd. results that when weather change is considered, the margin of error could be acceptable for some applications Copyright © showed 2018 Elsevier Ltd. only All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy This iserror an open accessdemand article under the CCthan BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) (the in annual was lower 20% for all weather scenarios considered). However, after introducing renovation th International Selection and peer-review under responsibility of the scientific committee of the 10 Conference onApplied Applied Energy (ICAE2018). Peer-review under responsibility of theupscientific committee of ICAE2018 – Theand 10threnovation International Conference on Energy. scenarios, the error value increased to 59.5% (depending on the weather scenarios combination considered). (ICAE2018). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: Organic Rankine cycle; heat exchanger; pressure drop decrease Organic in the number heating hours of pressure 22-139hdrop during the heating season (depending on the combination of weather and Keywords: Rankine of cycle; heat exchanger; renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +44(0)7563325654
address:author. [email protected] * E-mail Corresponding Tel.: +44(0)7563325654 Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.193
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1. Introduction As a cleaner burning gas, LNG is already the fuel of choice for part of transportation area. For transportation systems, LNG needs to be vaporized to a gaseous state before it enters the main engine. The exhaust gas from the engine and the latent energy from the vaporization process have a large amount of potential energy to utilize. In previous research, an ORC system has been built for dual reutilization of LNG latent energy and thermal waste energy in marine applications [3]. However, the pressure drop which occurs in the cycle has not yet been fully investigated. Lei et al [4] tried to make clear which kind of pressure losses can affect the system efficiency. They classified the losses into three categories of pressure losses in the cycle and found that the LPL (low pressure losses) are mainly responsible for efficiency decrease [4]. In this study, the model for the ORC system follows the structure of previous research and focuses on the pressure drop with different working fluids and the relationship of the working fluid to the performance of the cycle. To simplify the calculations, a few simplifications are made: The isotropic efficiency of the pumps and expanders are assumed to be constant values of 0.6 and 0.7 respectively. The mechanical efficiency of pumps and expanders is assumed to be 0.9. The turbines and pumps in the simulation are in 100% load conditions. The working fluid in the ORC will expand from the highest limited pressure to atmospheric pressure, which is 15bar to 1bar [3]. According to the actual LNG gas storage system [5], LNG will be evaporated from 5 bar 135℃ to 15 bar, then it will be expanded back to 5 bar. 2. Modelling and ORC system structure 2.1. ORC system with direct expansion of LNG The ORC system consists of two parts in this paper, which is shown in Fig. 1. The main cycle is a basic organic Rankine cycle. The pump is used to drive the working fluid and add its pressure from atmospheric pressure to 15 bar. A single turbine is in the cycle to use the evaporated working liquid to generate the power. The other part of the system is a direct expansion process of LNG, which is driven to go through the cold side of the condenser in the main cycle and acts as the heat sink for the main cycle and outputs PV work by another expander.
Fig. 1. Schematic of ORC system combined direct expansion of LNG There are three phase-changing stages, which occur in the evaporating side of the evaporator and the condensing and cooling sides of the condenser. It is noted that two-phase flow can cause a higher pressure drop because of the different flow rates of gas-phase flow and liquid-phase flow.
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(a)
3
(b)
Fig. 2. (a) Main ORC thermodynamic cycle with Ethylene; (b) The direct expansion process with LNG (CH4) From the Fig. 2, there are three phase-changing stage, which occur in the evaporating side of evaporator, both condensing side and cooling side of condenser. Because of the friction between the surface of liquid and vapor, there will be a higher pressure drop happened in the heat exchanger than the single phase one. 2.2. System efficiency and design In the theoretical analysis, the pressure drop in cycle is always related to the thermal efficiency, according to the efficiency equation: 𝜂𝜂𝑂𝑂𝑂𝑂𝑂𝑂 =
𝑊𝑊𝑜𝑜𝑜𝑜𝑜𝑜 −𝑊𝑊𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝
(1)
𝑄𝑄𝑖𝑖𝑖𝑖,𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡
which is used to calculate the system efficiency of ORCs. From the equation (2), it is obvious to see that if the pressure drop increases, the work done by the pump increases and the output work from the turbine decreases. This is because of the lower pressure ratio. This view is supported by Lei et al, who provided a detailed correlation to relate the thermal efficiency to the pressure [4], which is: 𝑑𝑑𝑑𝑑𝑂𝑂𝑂𝑂𝑂𝑂 = −
𝜂𝜂𝑡𝑡 𝑇𝑇1′𝑠𝑠
𝑞𝑞1 𝑇𝑇1′
𝑣𝑣1′ 𝑑𝑑Δ𝑃𝑃𝐻𝐻1 −
𝑣𝑣3
𝑞𝑞1 𝜂𝜂𝑝𝑝
𝑑𝑑Δ𝑃𝑃𝐻𝐻2 −
𝜂𝜂𝑡𝑡
𝑞𝑞1
𝑣𝑣1′𝑠𝑠 𝑑𝑑Δ𝑃𝑃𝐿𝐿
(2)
where ηt and ηp are the isentropic efficiency of the expander and pump. vi is the specific volume, q1 is the heat absorbed by working fluids in cycle and ΔPH1, ΔPH2 and ΔPL refer to the pressure drops occurring in the two-phase stages of the evaporator and the preheating stages in the evaporator and in the condenser. In this study, the evaporator and condenser are both plate heat exchangers (PHE). The design method of the PHEs in this paper is the logarithmic mean temperature difference (LMTD) method. A countercurrent flow model is selected for the PHEs, then the logarithmic mean temperature difference can be calculated using: Δ𝑇𝑇𝐿𝐿𝐿𝐿 =
(𝑇𝑇1 −𝑡𝑡2 )−(𝑇𝑇2 −𝑡𝑡1 ) 𝑇𝑇2 −𝑡𝑡1
and heat transfer coefficient can be calculated using: 1
h
=
1
ℎℎ
+
(3)
𝑇𝑇 −𝑡𝑡 𝐼𝐼𝐼𝐼 1 2
1
ℎ𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐
𝛿𝛿
+ + 𝐾𝐾
1
ℎ𝑐𝑐
+
1
ℎ𝑒𝑒𝑒𝑒𝑒𝑒
The subscripts ‘h’ and ’c’ mean the single-phase stage for the hot and cold side respectively. The overall heat transfer area is then obtained as:
(4)
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A=
721
Q
(5)
∆𝑇𝑇𝐿𝐿𝐿𝐿 ℎ
To check the accuracy of the results, the calculation is checked against the number of plates (np), (6) (7)
𝑛𝑛𝑝𝑝 = 𝑛𝑛ℎ + 𝑛𝑛𝑐𝑐 + 1 𝑛𝑛𝑝𝑝 𝐴𝐴𝑝𝑝 = 𝐴𝐴
where nh and nc are the number of flow pass in the PHE. The whole design process is repeated to determine the number of flow passes and heat transfer under certain heat transfer load and geometric parameters. Fig. 3 shows the entire process and assumed parameters. The overall heat transfer calculation is divided into several parts, which are the single phase stage, the two phase stage and the heat resistance of the plates. The correlations used for the overall heat transfer calculation are listed in Table 1. Table 1 Correlation for the calculation of heat transfer Stage of heat transfer Single-phase convection stage
Correlation h=
Condensation stage
𝑁𝑁𝑁𝑁×𝑘𝑘 𝐷𝐷𝑒𝑒
h𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 =
Evaporation stage
=
1
0.205𝑃𝑃𝑃𝑃 3(𝑓𝑓×𝑅𝑅𝑅𝑅 2 𝑠𝑠𝑠𝑠𝑠𝑠2𝛽𝛽)0.374 ×𝑘𝑘
𝑁𝑁𝑁𝑁×𝑘𝑘 𝐷𝐷𝑒𝑒
h′ =
=
𝐷𝐷𝑒𝑒 0.3𝑅𝑅𝑅𝑅𝑒𝑒𝑒𝑒 0.7 𝑃𝑃𝑟𝑟 0.33 (𝜇𝜇/𝜇𝜇𝑤𝑤 )×𝑘𝑘
𝐷𝐷𝑒𝑒 𝑅𝑅𝑅𝑅∙Pr(𝑓𝑓/2)(𝑘𝑘/𝐷𝐷𝑒𝑒 )
[6] [7]
2
1.07+12.7(𝑃𝑃𝑃𝑃 3 −1)(𝑓𝑓/2)0.5
h = (1.136𝐶𝐶𝐶𝐶 −0.9 + 66702𝐵𝐵𝐵𝐵 0.7 ∗ 𝐹𝐹𝑓𝑓1 )ℎ′[8]
where Reeq is the equivalent Reynold number. Co and Bo are the convection number and nucleate number respectively. The ORC utilizes the temperature difference between the exhaust gas and LNG to generate power. The thermodynamic process is modelled using an Engineering Equation Solver (EES). Three different working fluids for the cycle are tested to ascertain their influence on the pressure drop. To simplify the calculations, the isotropic efficiency for the pump and expanders are assumed to be 0.6 and 0.7 respectively and the mechanical efficiency is assumed to be 0.9 for both. The properties of the fluids are obtained from the EES and NIST’s database
, the geometric and thermal parameters are used to evaluate the pressure drop in it. Generally, the categories of pressure drop (∆P) in the PHE can be classified into four kinds: flow pressure drop, elevation pressure drop, momentum pressure drop and port pressure drop. Port pressure drop can be calculated by ∆𝑃𝑃𝑃𝑃 =
1.5𝐺𝐺𝑝𝑝 2 𝑛𝑛𝑝𝑝
(8)
2𝜌𝜌
The most common method of calculating flow pressure drop of single phase flow in PHEs is the Darcy-Weisbach equation. Δ𝑃𝑃 = 4𝑓𝑓
𝐿𝐿 𝜌𝜌𝑤𝑤2
𝐷𝐷𝑒𝑒
(9)
2
However, for two-phase flow, the Darcy equation cannot be used directly and the Lockhart-Martinelli (L-M) method has to be used to obtain the frictional pressure loss using a correction factor found by relation equations with the Martinelli factor [10]. ∆𝑃𝑃𝑓𝑓 = 4𝑓𝑓
𝐿𝐿 𝐺𝐺 2
𝐷𝐷𝑒𝑒 2𝜌𝜌
𝜑𝜑 2
Here φ2 is two-phase friction multiplier which can compute the single-phase flow pressure drop both vapor and liquid phase:
(10)
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𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑
5
𝑑𝑑𝑑𝑑
( )𝑓𝑓𝑓𝑓,𝑡𝑡𝑡𝑡 = ( )𝑓𝑓𝑓𝑓,𝑙𝑙 𝜑𝜑𝑙𝑙 2 = ( )𝑓𝑓𝑓𝑓,𝑔𝑔 𝜑𝜑𝑔𝑔 2 𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑
and is a function of X, the Martinelli parameter. X is defined as follows:
𝑋𝑋 2 =
The relations between φ2 and X are:
(11)
𝑑𝑑𝑑𝑑
𝑑𝑑𝑑𝑑 ) 𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓 𝑑𝑑𝑑𝑑 ( ) 𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓
(
(12)
(13) (14)
𝜑𝜑𝑔𝑔 2 = 1 + 𝑐𝑐𝑐𝑐 + 𝑋𝑋 2 𝑐𝑐
2
φ𝑙𝑙 = 1 + + 𝑋𝑋
1
𝑋𝑋 2
where the constant c is determined by the flow conditions [9], as shown in Table 2. Table 2. Comparison table for constant c and flow conditions Constant c Flow condition c=20 For liquid and vapor both turbulent c=12 For liquid-laminar, vapor-turbulent c=10 For liquid-laminar, vapor-laminar c=5 For liquid and vapor both laminar Zhong-zheng Wang and Zhen-Nan Zhao [10] showed the correlations for calculating the momentum and elevation pressure drops are ∆𝑃𝑃𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = 𝐺𝐺 2 {[
(1−𝑥𝑥2 )2
𝜌𝜌𝑙𝑙 (1−𝜑𝜑2 )
−
𝑥𝑥2 2
𝜌𝜌𝑣𝑣 𝜑𝜑2
]−[
(1−𝑥𝑥1 2 )
𝜌𝜌𝑙𝑙 (1−𝜑𝜑2 )
−
𝑥𝑥1 2
𝜌𝜌𝑣𝑣 𝜑𝜑2
∆𝑃𝑃𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 = 𝑔𝑔𝑔𝑔[𝜌𝜌𝑣𝑣 𝜑𝜑 + 𝜌𝜌𝑙𝑙 (1 − 𝜑𝜑)] The total pressure drop is obtained by summing Equation (8), (9), (15) and (16).
(15)
]}
(16)
2.3. Selection of working fluids Along with the geometric parameters of the PHE, the kind of working fluid also can affect the pressure drop in the PHE. Working fluids are operated from about their boiling point under atmospheric pressure to 200 oC. To take full advantage of the cryogenic energy of LNG, the fluids’ freezing point and boiling point are the key factors in selecting the working fluid. As in the previous research [3], the fluids are selected. These fluids and their properties are listed in Table 3 Table 3. Working fluids properties Freezing Point (oC) Ethylene C2H4 Propylene Isobutane R600a
-169 -185 -160
Boiling point (oC) -103.9 -47.78 -11.78
Critical Temperature (˚C) 9.2 91.7 134.7
Critical Pressure (bar) 50.42 46.65 36.4
Molar mass (g/mol) 28.05 42.08 58.12
3. Result and discussion Now that a simulation model has been established, the pressure drop in PHE can be evaluated. The three working fluids shown in Table 3 were tested in the condenser and the evaporator model described above. The mass flow rate increases from 0.004kg/s to 0.04kg/s.
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Fig. 3(a) (b) shows the working fluid’s and methane’s pressure drop in the model against the mass flow rate of working fluids. From the figure, it is clear that pressure drop is related to the mass flow rate with Propylene showing the highest pressure drop in both sides of the condenser and in the evaporator. To validate the prediction, Other researchers' predictions in plate heat exchangers will be cited here to compare the predicted value. The similar magnitude of the values shows that the prediction in this paper is persuasive. The cited researches are listed in Table 4 Table 4. Recent researches in PHE of two-phase flow’s pressure drop Author Working Fluid DongChan et al (2018)[11] R-1233zd(E) Amalfi et al (2016)[12] R245fa Vakili-Farahani et al (2014)[12] R245fa Kitti and Somchai (2010)[13] Air-water
Pressure Drop (kPa) 2~28 4~25 6~23 8~70
Fig. 4(a) (b) show the influence of pressure drops caused by different mass flow rate with different working fluids on systems’ efficiency.
PRESSURE DROP (KPA)
Ethlyene 40 35 30 25 20 15 10 5 0
4
8
12
Propylene
16
20
24
R600a
28
32
36
40
MASS FLOW RATE (G/S)
(a) Ethlyene
Propylene
R600a
PRESSURE DROP (KPA)
12 10 8 6 4 2 0
4
8
12
16
20
24
28
32
36
40
MASS FLOW RATE (G/S)
(b) Fig. 3. (a) Pressure drop of working fluids in model (b) Pressure drop of methane in simulation
Author name / Energy Procedia 00 (2018) 000–000
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Ethlyene
Propylene
R600a
18 16
EFFICIENCY(%)
14 12 10 8 6 4 2 0
4
8
12
16
20
24
28
32
36
40
36
40
MASS FLOW RATE (G/S)
(a) Ethylene
Propylene
R600a
25.39 25.38 EFFICIENCY（%）
25.37 25.36 25.35 25.34 25.33 25.32 25.31 25.3
4
8
12
16
20
24
28
32
MASS FLOW RATE (G/S)
(b) Fig.4. (a) ORC’s efficiency (b) Expansion efficiency of LNG As shown in Fig 4, the maximum simulation efficiency is 15.57% in the ORC system and 25.4% in LNG’s expansion. The efficiency for both the ORC and direct expansion decrease as pressure drop increases. Ethylene, is shown to be the most suitable working fluid as it achieves the highest efficiency over the range of mass flow rates (from 15.53% to 14.46%). The Propylene achieves efficiencies ranging from 12.33% to 10.23%. R600a has the lowest system efficiencies ranging from 10.1% to 8.4%. It is noted that the pressure drops caused by Ethylene and R600a are similar. However, Ethylene has a better working temperature range. The decrease in efficiency over the full range of mass flow rates for LNG expansion is similar for each working fluid, around 0.1%. The lowest value is obtained by Propylene, which is 25.33%
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Yi Li et al. / Energy Procedia 158 (2019) 718–725 Author name / Energy Procedia 00 (2018) 000–000
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4. Conclusions According Equations (1) & (2), pressure drops have a negative impact on the performance of ORC systems. This paper introduces a way to evaluate pressure drop inside a PHE and analyze its influence on system efficiency. The conclusions of the study are: Pressure drop increases with mass flow rate. Propylene shows the greatest drop in efficiency over the total range of mass flow rates. The efficiency of direct expansion decreases as the pressure drop increases. Ethylene and R600a show similar pressure drops but R600a shows the greatest drop in efficiency over the range of mass flow rates. This is due to the temperature range of the fluids. References [1] Shell (2017) shell-lng-outlook2017-slides-master-march2017. Shell. Available at: (Accessed: 15 December 2017). [2] IGU-World LNG Report-2015 Edition (2015) International gas union. Available at: (Accessed: 15 December 2017). [3] Tsougranis, E. and Wu, D. (2017) Dual Reutilization of LNG Cryogenic Energy and Thermal Waste Energy with Organic Rankine Cycle in Marine Applications. Energy Procedia, 142, pp. 1401-1406. [4] Lei, B., Wu, Y., Ma, C., Wang, W., and Zhi, R. (2017) Theoretical analyses of pressure losses in organic Rankine cycles. Energy Conversion and Management, 153, pp. 157-162. [5] Wärtsilä Ship Power (2013) Gas Storage and supply systems. Available at: (Accessed: 10 May 2018). [6] Martin, H. (1996) A theoretical approach to predict the performance of chevron-type plate heat exchangers. Chemical Engineering and Processing: Process Intensification, 35(4), pp. 301-310. [7] Kumar, H. (1983) CONDENSATION DUTIES IN PLATE HEAT EXCHANGERS. Institution of Chemical Engineers Symposium Series, 75, PP. 478-509 [8] Kandlikar, S. (1991) Development of a Flow Boiling Map for Subcooled and Saturated Flow Boiling of Different Fluids Inside Circular Tubes. Journal of Heat Transfer, 113(1), p. 190. [9] Chisholm, D. (1967) A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow. International Journal of Heat and Mass Transfer, 10(12), pp. 1767-1778. [10] WANG, Z. and ZHAO, Z. (1993) Analysis of Performance of Steam Condensation Heat Transfer and Pressure Drop in Plate Condensers. Heat Transfer Engineering, 14(4), pp. 32-41. [11] Lee, D., Kim, D., Park, S., Lim, J. and Kim, Y. (2018). Evaporation heat transfer coefficient and pressure drop of R-1233zd(E) in a brazed plate heat exchanger. Applied Thermal Engineering, 130, pp.1147-1155. [12] Grabenstein, V., Polzin, A., and Kabelac, S. (2017) Experimental investigation of the flow pattern, pressure drop and void fraction of two-phase flow in the corrugated gap of a plate heat exchanger. International Journal of Multiphase Flow, 91, pp. 155-169. [13] Nilpueng, K. and Wongwises, S. (2010) Two-phase gas–liquid flow characteristics inside a plate heat exchanger. Experimental Thermal and Fluid Science, 34(8), pp. 1217-1229.