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The application analysis of jet pump in heating system
Available Available online online at at www.sciencedirect.com www.sciencedirect.com
ScienceDirect
Available online at www.sciencedirect.com Procedia Procedia Engineering00 Engineering00 (2017) (2017) 000–000 000–000
ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 2208–2214
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
The application analysis of jet pump in heating system a,b,c, **, Qunqun Zhan aa, Yongan Liabb Xuelai Liua,b,c, aSchool of Thermal Engineering, Shandong Jianzhu University, Jinan,250101 China School of Thermal Engineering, Shandong Jianzhu University, Jinan,250101 China Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Ministry Ministry of of Education, Education, Jinan, Jinan, 250101China 250101China cc Shandong Key Laboratory of Renewable Energy Technologies for Buildings, Jinan, Shandong Key Laboratory of Renewable Energy Technologies for Buildings, Jinan, 250101China 250101China a
bb
Abstract Abstract With With the the more more and and more more extensive extensive application application of of jet jet pump pump in in heating heating system, system, the the research research of of jet jet pump pump is is becoming becoming more more and and more more important. important. This This paper paper studies studies the the occasions occasions of of jet jet pump pump in in the the heating heating system system and and takes takes aa heating heating pipe pipe network network of of Ji'nan Ji'nan city city as as an an example example to to analyze analyze the the energy energy saving saving effect effect of of jet jet pump, pump, the the jet jet pump pump has has obtained obtained good good economic economic benefit benefit and and energy energy saving application in heating system. saving application in heating system. © 2017 2017 The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. © © 2017 The The Authors. Published by Elsevier Ltd. Peer-review under under responsibility responsibility of of the the scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Peer-review Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Conditioning. Conditioning. Air Conditioning. Keywords: Keywords: Jet Jet pump; pump; Heating Heating system; system; Application; Application; Energy-saving Energy-saving
Preface G.Zeuner, a German scholar, proposed the jet theory and theoretical basis of jet pump’s design in 1860s. Then the jet pumps had been widely developed and were being used more and more in practice. In recent years, with the rapid development of central heating system, jet pump has been widely used because of its simple structure, reliable operation and less power consumption. Therefore, it is necessary to make a thorough study of the structural property and operating principle of the jet pump. 1 Principle and characteristics of jet pump * * Corresponding Corresponding author. author. E-mail E-mail address: address: [email protected] [email protected] 1877-7058 1877-7058 © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review Peer-review under under responsibility responsibility ofthe ofthe scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Conditioning. Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.050
2
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
2209
A jet pump is a device that doesn’t directly consume mechanical energy. It uses the jet of high-pressure working fluid to transport low-energy jet fluid. The structure of the jet pump is shown in Figure 1, it consists of a nozzle, a water intake chamber, a mixing chamber and a diffusion tube.
Fig. 1 Structure drawing of jet pump
Jet pump uses a high pressure working fluid energy to transport low energy driving fluid, different pressure of two fluids mixes in the mixing chamber and exchange the energy, finally mixes in a mixed fluid between the two fluid pressure discharged from the diffusion chamber. 2 Several applications of jet pump in heating system 2.1 Jet pump is installed at the thermal entrance In heating system, if the jet pump installed at the thermal entrance, its function is similar to the mixing pump, a heating way that mixing with high temperature water supply and low temperature backwater. It uses the increasing speed at the nozzle to reduce the pressure, then the low temperature backwater is drawn into the water diversion chamber and mixed with the water supply, the mixed fluid is supplied to each heat user after reach a suitable temperature. But when the jet pump is installed at the entrance of the heat, it is necessary to ensure that the pressure of the water supply can reach the operating conditions of the injection pump, and only when the external network pressure meets the requirements the jet pump can operate under the design efficiency. Water jet pump not only has a very simple structure, but also installed in the heating system of the pipe network program is very simple, and it is also convenient to connect with other equipment. Fig. 3 is a schematic diagram of a jet pump in a distributed heating system. But the jet pump is rarely installed at the thermal inlet in practical applications, because the jet pump needs greater pressure, about 80~120kPa, the heating radius of the two stage network is smaller generally, and the supply and return water pressure is not easy to meet the requirements of jet pump pressure, thereby limiting the application of jet pump in heating system.
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Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
3
Fig. 3 Schematic diagram of a distributed heating system with a jet pump
2.2 Jet pump installed in high and low area direct connection system In recent years, with the increasing of building height, the problems of high and low area pipe network should be considered in the same heating system, when the system heating for high area users, usually installs pressurized water pump in the water supply pipe to increase pipe’s pressure, the pressure pump provides a small part of the pressure to overcome resistance of uses, which will make the high area’s return water pressure is relatively large, in order to make the heating pipe network operate steadily, it is necessary to install a throttle on the return pipe to drain out the excess pressure head, resulting in a waste of energy in vain. In order to use this part of energy efficiently, we can install jet pump on the return pipe of high area system, so that increasing the hydraulic stability of the whole pipe network without consuming other extra energy, using the energy wasted in throttle valves originally to achieve energy-saving effect. As shown in Figure 4, the jet pump is installed at the intersection of the return pipe of high system and the water supply pipe (low users’ entrance).Using return water of high area with heavy pressure to mix with water supply of pipe network for low area users. This system has the effect of throttle to return water of high area, while the user of low area utilize the energy of high area return water in directly .It can improve the stability of heating pipe network and the energy-saving effect is obvious. The pressure diagram is shown in Figure 5.
Fig. 4 A system diagram of a jet pump installed at the entrance of a low area user
Fig. 5 A pressure diagram of a jet pump installed at the entrance of a low area user
As shown in Figure 5, after installing pressure pump in the water supply pipe network of high area and
4
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
2211
overcoming the network and high user pressure head, the pressure drops to a point. The pressure drops to B points after installing jet pump, then the system supplies water to the lower users and overcomes pipe network resistance and user pressure head, the pressure drops to C points and backs to the main return water pipe. 2.3 Jet pump installed in the heating system with radiator and ground radiation Nowadays, more and more users adopt comfortable ground radiation heating, which the temperature of water supply and return is 60/50℃,but the temperature of water supply and return of radiator heating is 85/60℃.If the two terminal forms exist in one heating system, the users with floor heating can be solved by jet pump. As shown in Figure 6.
Fig. 6 Schematic diagram of heating system with radiator and ground radiation
As shown in Figure 6, installing jet pump at the entrance of floor heating users and the temperature of water supply and return designs by demand of radiator users, which pumping ground return water by water supply of two nets, then supplying to users after mixing. For the heating system with radiator and ground radiation, after the jet pump is installed, not only the flow rate of the pipe network of the ground heating user is reduced, the pipe material is saved, but also the system can be operated without rebuilding the whole pipe network and the initial investment is saved. 3 Energy saving analysis of jet pump in distributed heating system Because of the heat exchanging station, there are many problems appear such as poor heat transfer effect and large heat loss, affect the heating effect seriously. Therefore, we can use jet pump instead of the heat exchanger and the user circulating water pump by making use of the large pressure difference between primary and two networks. It can not only improve the temperature difference between supply and return water of the primary network, but also increase the heat exchange effect, which solves the problem that the heat demand of the heat user can not be satisfied fundamentally. In order to analyze the energy saving effect of jet pump in heating system, this paper takes a distributed heating network in a boiler room in Ji'nan city as an example, assuming that the network has 5 equal distance distribution cell users, and each thermal user needs equal pressure head,100kPa, and fifth thermal users are the most disadvantaged users. A network of supply and return water pipe network total length is 5000m, two network supply and return water pipe network is 500m, pipe friction resistance is 60 Pa/m, local resistance is 30% of the along resistance, the pump efficiency is 70%. According to the laws of Herb Roots, the theoretical shaft power of circulating water pump in traditional heating mode can be calculated by formula (1):
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
2212
N=
5
N0 QH = η ⋅ 367 η ⋅ 367
where
（1）
Q is flow rate of circulating pump of heat source, m3/h; H is the head of the circulating pump of heat source,
m; η is water pump efficiency, 70%; N 0 is shaft power of circulating water pump calculated by the law of Herb Roots，kW; N is shaft power of circulating water pump, kW.
H = ΔH s + ΔH z + ΔH y + ΔH j
（2）
where ΔH s is internal pressure loss of heat source, 15m; ΔH z is pressure head of user, 10m; ΔH y is total along resistance loss of the most adverse loop, m; ΔH j is local resistance loss, m. This article sets up three schemes to analysis, scheme 1 is indirect connection system by using plate heat exchanger, the supply and return water temperature of a network is 120/70 ℃ ,the supply and return water temperature of two nets is 85/60℃, designed total circulating water is 150t/h, each cell corresponds to a heat exchanger station. According to formula (1) and (2) calculates the shaft power of the first stage circulating water pump (heat source pump):
N=
150t / h × (15 + 3 × 1.3) m = 11.04 KW 0.7 × 367
Because of the existence of the heat exchanger, the resistance loss of the 8~10m must be considered. Each grade circulating water pump’s shaft power is shown in the following table: Table 1 grade circulating water pump shaft power of indirect connection system with heat exchanger user Grade circulating water pump shaft power/kW
1
2
3
4
5
Total power
1.39
2.3
3.21
4.12
5.03
16.05
The shaft power of two grade network heat user circulating water pump is:
N=
30t / h × (10 + 3 × 1.3) m = 1.62 kW 0.7 × 367
So the total energy consumption of circulating water pump of scheme 1 is: 11.04+16.05+1.62×5=35.19kW Scheme 2 is direct connection system by using mixing pump, the supply and return water temperature of a network is 120/70℃,the supply and return water temperature of two nets is 95/70℃, each user corresponds to a mixing station. It is known by the formula Q = cmΔt , the flow is m = G
=
Q , in the same amount of heating, the greater cΔt
the temperature difference, the smaller the flow. So the total circulating water of scheme 2 is 120t/h. The shaft power of the first stage circulating water pump (heat source pump) is:
6
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
N=
2213
120t / h × (15 + 3 × 1.3) m = 8.83 kW 0.7 × 367
Each grade circulating water pump’s shaft power is shown in the following table: Table 2 grade circulating pump shaft power of direct connection system with mixing water user Grade circulating water pump shaft power/kW
1
2
3
4
5
Total power
0.46
1.37
2.28
3.19
4.1
11.4
The shaft power of two grade network heat user circulating water pump is:
N=
24t / h × (10 + 3 ×1.3) m = 1.3 kW 0.7 × 367
So the total energy consumption of circulating water pump of scheme 2 is: 8.83+11.4+1.3×5=26.73kW Scheme 3 is direct connection system by using jet pump, the supply and return water temperature is 120/95/70℃,the energy is no need to set two level network heat user circulating water pump because of the existence of jet pump, so the total energy consumption of circulating water pump of scheme 3 is 8.83+11.4=20.23kW. From the above analysis we can see that, the total energy consumption of circulating water pump of direct connection system by using jet pump is smaller than two other systems. Moreover, the heat exchanger will appear the circumstances of occlusion during the actual operation, so as to increase the local resistance and reduce the heat exchange efficiency. Therefore, the jet pump applies in the heating system can not only avoid the heat loss caused by the heat exchange of the heat exchanger, but also eliminate the energy consumption of the circulating water pump of the two network heat users, which playing a role of energy saving. 4 Conclusion In the heating system, the jet pump has remarkable energy-saving benefits compared with the heat exchanger and water mixer, and it is no need to set two level network heat user circulating water pump, so this system can reduce the initial investment and have good economic benefits. The jet pump is especially suitable for the pipe network system with high and low district. Under the premise of not consuming any additional energy, the energy consumption of the throttle valve is effectively utilized, and the stability of the whole heating system is improved. Also it suitable for the heating system with radiator heating and floor heating, it improves the heating capacity of network and save energy consumption. At the same time, this system can also avoid the troubles of the overall reconstruction of the pipe network and save the pipe consumption. On the other hand, the jet pump’s access direction is same with the trend of pipe network in the heating system, so we don’t need to consider the problem because of connection and it will not bring extra trouble to the construction. There for, the jet pump is applied more and more widely in the heating system. Acknowledgement Thanks to the ministry of Housing and Urban-Rural science and technology development plan (2014 - K1-039) and Shandong Jianzhu university doctor fund project (XNBS1221) support Reference [1]Zhaoyu Shi. Development of adjustable water jet pump [J].District Heating, 2000.2:10-13
2214
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
7
[2]Hongqi Lu. Theory and application of injection technology [M].Wuhan: Wuhan university press, 2004 [3]Ping He, SUN Gang et al. Heating engineering (Fourth Edition)[M].Beijing: China Building Industry Press,2009 [4]Weiying Ren. Application and numerical simulation of water jet pump in a new heating system [D].Taiyuan: Taiyuan University of Technology, 2011 [5]Fei Wang, Zhihui Chen, Yuliang Ding. The application of water jet pump in the high area direct-connected in heating-system [J].Building Energy & Environment, 2007, 26(5): 64-67 [6]Chaoqian Wang, Xuelai Liu. Energy saving analysis of distributed variable frequency pump heating system [J]. Science & Technology Information, 2012 (10): 143-143
ScienceDirect
Available online at www.sciencedirect.com Procedia Procedia Engineering00 Engineering00 (2017) (2017) 000–000 000–000
ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 2208–2214
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
The application analysis of jet pump in heating system a,b,c, **, Qunqun Zhan aa, Yongan Liabb Xuelai Liua,b,c, aSchool of Thermal Engineering, Shandong Jianzhu University, Jinan,250101 China School of Thermal Engineering, Shandong Jianzhu University, Jinan,250101 China Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Ministry Ministry of of Education, Education, Jinan, Jinan, 250101China 250101China cc Shandong Key Laboratory of Renewable Energy Technologies for Buildings, Jinan, Shandong Key Laboratory of Renewable Energy Technologies for Buildings, Jinan, 250101China 250101China a
bb
Abstract Abstract With With the the more more and and more more extensive extensive application application of of jet jet pump pump in in heating heating system, system, the the research research of of jet jet pump pump is is becoming becoming more more and and more more important. important. This This paper paper studies studies the the occasions occasions of of jet jet pump pump in in the the heating heating system system and and takes takes aa heating heating pipe pipe network network of of Ji'nan Ji'nan city city as as an an example example to to analyze analyze the the energy energy saving saving effect effect of of jet jet pump, pump, the the jet jet pump pump has has obtained obtained good good economic economic benefit benefit and and energy energy saving application in heating system. saving application in heating system. © 2017 2017 The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. © © 2017 The The Authors. Published by Elsevier Ltd. Peer-review under under responsibility responsibility of of the the scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Peer-review Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Conditioning. Conditioning. Air Conditioning. Keywords: Keywords: Jet Jet pump; pump; Heating Heating system; system; Application; Application; Energy-saving Energy-saving
Preface G.Zeuner, a German scholar, proposed the jet theory and theoretical basis of jet pump’s design in 1860s. Then the jet pumps had been widely developed and were being used more and more in practice. In recent years, with the rapid development of central heating system, jet pump has been widely used because of its simple structure, reliable operation and less power consumption. Therefore, it is necessary to make a thorough study of the structural property and operating principle of the jet pump. 1 Principle and characteristics of jet pump * * Corresponding Corresponding author. author. E-mail E-mail address: address: [email protected] [email protected] 1877-7058 1877-7058 © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review Peer-review under under responsibility responsibility ofthe ofthe scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Conditioning. Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.050
2
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
2209
A jet pump is a device that doesn’t directly consume mechanical energy. It uses the jet of high-pressure working fluid to transport low-energy jet fluid. The structure of the jet pump is shown in Figure 1, it consists of a nozzle, a water intake chamber, a mixing chamber and a diffusion tube.
Fig. 1 Structure drawing of jet pump
Jet pump uses a high pressure working fluid energy to transport low energy driving fluid, different pressure of two fluids mixes in the mixing chamber and exchange the energy, finally mixes in a mixed fluid between the two fluid pressure discharged from the diffusion chamber. 2 Several applications of jet pump in heating system 2.1 Jet pump is installed at the thermal entrance In heating system, if the jet pump installed at the thermal entrance, its function is similar to the mixing pump, a heating way that mixing with high temperature water supply and low temperature backwater. It uses the increasing speed at the nozzle to reduce the pressure, then the low temperature backwater is drawn into the water diversion chamber and mixed with the water supply, the mixed fluid is supplied to each heat user after reach a suitable temperature. But when the jet pump is installed at the entrance of the heat, it is necessary to ensure that the pressure of the water supply can reach the operating conditions of the injection pump, and only when the external network pressure meets the requirements the jet pump can operate under the design efficiency. Water jet pump not only has a very simple structure, but also installed in the heating system of the pipe network program is very simple, and it is also convenient to connect with other equipment. Fig. 3 is a schematic diagram of a jet pump in a distributed heating system. But the jet pump is rarely installed at the thermal inlet in practical applications, because the jet pump needs greater pressure, about 80~120kPa, the heating radius of the two stage network is smaller generally, and the supply and return water pressure is not easy to meet the requirements of jet pump pressure, thereby limiting the application of jet pump in heating system.
2210
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
3
Fig. 3 Schematic diagram of a distributed heating system with a jet pump
2.2 Jet pump installed in high and low area direct connection system In recent years, with the increasing of building height, the problems of high and low area pipe network should be considered in the same heating system, when the system heating for high area users, usually installs pressurized water pump in the water supply pipe to increase pipe’s pressure, the pressure pump provides a small part of the pressure to overcome resistance of uses, which will make the high area’s return water pressure is relatively large, in order to make the heating pipe network operate steadily, it is necessary to install a throttle on the return pipe to drain out the excess pressure head, resulting in a waste of energy in vain. In order to use this part of energy efficiently, we can install jet pump on the return pipe of high area system, so that increasing the hydraulic stability of the whole pipe network without consuming other extra energy, using the energy wasted in throttle valves originally to achieve energy-saving effect. As shown in Figure 4, the jet pump is installed at the intersection of the return pipe of high system and the water supply pipe (low users’ entrance).Using return water of high area with heavy pressure to mix with water supply of pipe network for low area users. This system has the effect of throttle to return water of high area, while the user of low area utilize the energy of high area return water in directly .It can improve the stability of heating pipe network and the energy-saving effect is obvious. The pressure diagram is shown in Figure 5.
Fig. 4 A system diagram of a jet pump installed at the entrance of a low area user
Fig. 5 A pressure diagram of a jet pump installed at the entrance of a low area user
As shown in Figure 5, after installing pressure pump in the water supply pipe network of high area and
4
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
2211
overcoming the network and high user pressure head, the pressure drops to a point. The pressure drops to B points after installing jet pump, then the system supplies water to the lower users and overcomes pipe network resistance and user pressure head, the pressure drops to C points and backs to the main return water pipe. 2.3 Jet pump installed in the heating system with radiator and ground radiation Nowadays, more and more users adopt comfortable ground radiation heating, which the temperature of water supply and return is 60/50℃,but the temperature of water supply and return of radiator heating is 85/60℃.If the two terminal forms exist in one heating system, the users with floor heating can be solved by jet pump. As shown in Figure 6.
Fig. 6 Schematic diagram of heating system with radiator and ground radiation
As shown in Figure 6, installing jet pump at the entrance of floor heating users and the temperature of water supply and return designs by demand of radiator users, which pumping ground return water by water supply of two nets, then supplying to users after mixing. For the heating system with radiator and ground radiation, after the jet pump is installed, not only the flow rate of the pipe network of the ground heating user is reduced, the pipe material is saved, but also the system can be operated without rebuilding the whole pipe network and the initial investment is saved. 3 Energy saving analysis of jet pump in distributed heating system Because of the heat exchanging station, there are many problems appear such as poor heat transfer effect and large heat loss, affect the heating effect seriously. Therefore, we can use jet pump instead of the heat exchanger and the user circulating water pump by making use of the large pressure difference between primary and two networks. It can not only improve the temperature difference between supply and return water of the primary network, but also increase the heat exchange effect, which solves the problem that the heat demand of the heat user can not be satisfied fundamentally. In order to analyze the energy saving effect of jet pump in heating system, this paper takes a distributed heating network in a boiler room in Ji'nan city as an example, assuming that the network has 5 equal distance distribution cell users, and each thermal user needs equal pressure head,100kPa, and fifth thermal users are the most disadvantaged users. A network of supply and return water pipe network total length is 5000m, two network supply and return water pipe network is 500m, pipe friction resistance is 60 Pa/m, local resistance is 30% of the along resistance, the pump efficiency is 70%. According to the laws of Herb Roots, the theoretical shaft power of circulating water pump in traditional heating mode can be calculated by formula (1):
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
2212
N=
5
N0 QH = η ⋅ 367 η ⋅ 367
where
（1）
Q is flow rate of circulating pump of heat source, m3/h; H is the head of the circulating pump of heat source,
m; η is water pump efficiency, 70%; N 0 is shaft power of circulating water pump calculated by the law of Herb Roots，kW; N is shaft power of circulating water pump, kW.
H = ΔH s + ΔH z + ΔH y + ΔH j
（2）
where ΔH s is internal pressure loss of heat source, 15m; ΔH z is pressure head of user, 10m; ΔH y is total along resistance loss of the most adverse loop, m; ΔH j is local resistance loss, m. This article sets up three schemes to analysis, scheme 1 is indirect connection system by using plate heat exchanger, the supply and return water temperature of a network is 120/70 ℃ ,the supply and return water temperature of two nets is 85/60℃, designed total circulating water is 150t/h, each cell corresponds to a heat exchanger station. According to formula (1) and (2) calculates the shaft power of the first stage circulating water pump (heat source pump):
N=
150t / h × (15 + 3 × 1.3) m = 11.04 KW 0.7 × 367
Because of the existence of the heat exchanger, the resistance loss of the 8~10m must be considered. Each grade circulating water pump’s shaft power is shown in the following table: Table 1 grade circulating water pump shaft power of indirect connection system with heat exchanger user Grade circulating water pump shaft power/kW
1
2
3
4
5
Total power
1.39
2.3
3.21
4.12
5.03
16.05
The shaft power of two grade network heat user circulating water pump is:
N=
30t / h × (10 + 3 × 1.3) m = 1.62 kW 0.7 × 367
So the total energy consumption of circulating water pump of scheme 1 is: 11.04+16.05+1.62×5=35.19kW Scheme 2 is direct connection system by using mixing pump, the supply and return water temperature of a network is 120/70℃,the supply and return water temperature of two nets is 95/70℃, each user corresponds to a mixing station. It is known by the formula Q = cmΔt , the flow is m = G
=
Q , in the same amount of heating, the greater cΔt
the temperature difference, the smaller the flow. So the total circulating water of scheme 2 is 120t/h. The shaft power of the first stage circulating water pump (heat source pump) is:
6
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 X.L Liu et al. / Procedia Engineering00 (2017) 000–000
N=
2213
120t / h × (15 + 3 × 1.3) m = 8.83 kW 0.7 × 367
Each grade circulating water pump’s shaft power is shown in the following table: Table 2 grade circulating pump shaft power of direct connection system with mixing water user Grade circulating water pump shaft power/kW
1
2
3
4
5
Total power
0.46
1.37
2.28
3.19
4.1
11.4
The shaft power of two grade network heat user circulating water pump is:
N=
24t / h × (10 + 3 ×1.3) m = 1.3 kW 0.7 × 367
So the total energy consumption of circulating water pump of scheme 2 is: 8.83+11.4+1.3×5=26.73kW Scheme 3 is direct connection system by using jet pump, the supply and return water temperature is 120/95/70℃,the energy is no need to set two level network heat user circulating water pump because of the existence of jet pump, so the total energy consumption of circulating water pump of scheme 3 is 8.83+11.4=20.23kW. From the above analysis we can see that, the total energy consumption of circulating water pump of direct connection system by using jet pump is smaller than two other systems. Moreover, the heat exchanger will appear the circumstances of occlusion during the actual operation, so as to increase the local resistance and reduce the heat exchange efficiency. Therefore, the jet pump applies in the heating system can not only avoid the heat loss caused by the heat exchange of the heat exchanger, but also eliminate the energy consumption of the circulating water pump of the two network heat users, which playing a role of energy saving. 4 Conclusion In the heating system, the jet pump has remarkable energy-saving benefits compared with the heat exchanger and water mixer, and it is no need to set two level network heat user circulating water pump, so this system can reduce the initial investment and have good economic benefits. The jet pump is especially suitable for the pipe network system with high and low district. Under the premise of not consuming any additional energy, the energy consumption of the throttle valve is effectively utilized, and the stability of the whole heating system is improved. Also it suitable for the heating system with radiator heating and floor heating, it improves the heating capacity of network and save energy consumption. At the same time, this system can also avoid the troubles of the overall reconstruction of the pipe network and save the pipe consumption. On the other hand, the jet pump’s access direction is same with the trend of pipe network in the heating system, so we don’t need to consider the problem because of connection and it will not bring extra trouble to the construction. There for, the jet pump is applied more and more widely in the heating system. Acknowledgement Thanks to the ministry of Housing and Urban-Rural science and technology development plan (2014 - K1-039) and Shandong Jianzhu university doctor fund project (XNBS1221) support Reference [1]Zhaoyu Shi. Development of adjustable water jet pump [J].District Heating, 2000.2:10-13
2214
Xuelai Liu et al. / Procedia Engineering 205 (2017) 2208–2214 XL Liu et al. / Procedia Engineering 00 (2017) 000–000
7
[2]Hongqi Lu. Theory and application of injection technology [M].Wuhan: Wuhan university press, 2004 [3]Ping He, SUN Gang et al. Heating engineering (Fourth Edition)[M].Beijing: China Building Industry Press,2009 [4]Weiying Ren. Application and numerical simulation of water jet pump in a new heating system [D].Taiyuan: Taiyuan University of Technology, 2011 [5]Fei Wang, Zhihui Chen, Yuliang Ding. The application of water jet pump in the high area direct-connected in heating-system [J].Building Energy & Environment, 2007, 26(5): 64-67 [6]Chaoqian Wang, Xuelai Liu. Energy saving analysis of distributed variable frequency pump heating system [J]. Science & Technology Information, 2012 (10): 143-143