ANALYTICAL STUDY ON THE HEATING PERFORMANCE OF A MULTI-TYPE HEAT PUMP SYSTEM WITH n-INDOOR UNITS

2011 ◽  
Vol 19 (01) ◽  
pp. 25-36 ◽  
Author(s):  
JONG WON CHOI ◽  
IL HWAN LEE ◽  
MIN SOO KIM
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Lumped Parameter Model ◽  
Distributed Model ◽  
Experimental Conditions ◽  
Pump System ◽  
Heat Pump System ◽  
Heating Performance ◽  
Lumped Parameter ◽  
Expansion Valve

This paper presents the steady-state heating performance of a multi-type heat pump system. The compressor and expansion valves are described by a lumped parameter model for its rapid and prompt response to the disturbances compared to those of the heat exchangers. Fully distributed model (or spatially dependent model) is used for the evaporator and condenser since the lumped method does not guarantee enough accuracy in estimating the performance of heat exchangers with phase change. Most researches on the numerical simulation in heat pump system focuses on the precise modeling for the steady or transient states while few researches on the simulations consider the relationships among several indoor units, expansion valve openings and compressor speed in multi-type heat pump system. In this study, the heating performance of a multi-type heat pump system using R410A with three indoor units is simulated for the investigation of system characteristics and the simulation results are verified for several experimental conditions. Finally, the simulation technique is extended to the system with n-indoor units.

Surge Onset in Turbo Heat Pumps

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Jieun Song ◽  
Jung Chan Park ◽  
Kil Young Kim ◽  
Jinhee Jeong ◽  
Seung Jin Song
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Working Fluid ◽  
Pump System ◽  
Heat Pump System ◽  
Linearized Stability ◽  
Stability Model ◽  
Expansion Valve ◽  
Mass Spring

A typical turbo heat pump system consists of a centrifugal compressor, expansion valve, and two heat exchangers—a condenser and evaporator. Compared to a gas turbine, a turbo heat pump introduces additional complexities because it is a two-phase closed-loop system with heat exchange using a real gas/liquid (refrigerant) as the working fluid. For the first time, surge onset in such systems has been physically, analytically, and experimentally investigated. This study analytically investigates the physical mechanisms of surge onset in turbo heat pumps. From an existing nonlinear turbo heat pump surge model, the turbo heat pump is viewed as a mass-spring-damper system with two inertias, two dampers, and four springs which is then further simplified to a single degree-of-freedom system. Surge onset occurs when the system damping becomes zero and depends not only the compressor but also on the ducts, heat exchangers, and expansion valve. Alternatively, a new stability model has been developed by applying a linearized small perturbation method to the nonlinear turbo heat pump surge model. When the new linear stability model is applied to a conventional open loop compression system (e.g., a turbocharger), predictions identical to those of Greitzer's model are obtained. In addition, surge onset has been experimentally measured in two turbo heat pumps. A comparison of the predictions and measurements shows that the mass-spring-damper model and the linearized stability model can accurately predict the turbo heat pump surge onset and the mass-spring-damper model can explain the turbo heat pump surge onset mechanisms and parametric trends in turbo heat pumps.

scholarly journals Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1762 ◽  
Author(s):  
Zhe Wang ◽  
Fenghui Han ◽  
Yulong Ji ◽  
Wenhua Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Transfer Model ◽  
Enhanced Heat Transfer ◽  
Pump System ◽  
Heat Pump System ◽  
Tube Heat Exchanger ◽  
Exergy Transfer

A marine seawater source heat pump is based on the relatively stable temperature of seawater, and uses it as the system’s cold and heat source to provide the ship with the necessary cold and heat energy. This technology is one of the important solutions to reduce ship energy consumption. Therefore, in this paper, the heat exchanger in the CO2 heat pump system with graphene nano-fluid refrigerant is experimentally studied, and the influence of related factors on its heat transfer enhancement performance is analyzed. First, the paper describes the transformation of the heat pump system experimental bench, the preparation of six different mass concentrations (0~1 wt.%) of graphene nanofluid and its thermophysical properties. Secondly, this paper defines graphene nanofluids as beneficiary fluids, the heat exchanger gains cold fluid heat exergy increase, and the consumption of hot fluid heat is heat exergy decrease. Based on the heat transfer efficiency and exergy efficiency of the heat exchanger, an exergy transfer model was established for a seawater source of tube heat exchanger. Finally, the article carried out a test of enhanced heat transfer of heat exchangers with different concentrations of graphene nanofluid refrigerants under simulated seawater constant temperature conditions and analyzed the test results using energy and an exergy transfer model. The results show that the enhanced heat transfer effect brought by the low concentration (0~0.1 wt.%) of graphene nanofluid is greater than the effect of its viscosity on the performance and has a good exergy transfer effectiveness. When the concentration of graphene nanofluid is too high, the resistance caused by the increase in viscosity will exceed the enhanced heat transfer gain brought by the nanofluid, which results in a significant decrease in the exergy transfer effectiveness.

Experimental Investigation on Heating Performance of Newly Designed Air Source Heat Pump System for Electric Vehicles

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Kang Li ◽  
Jun Yu ◽  
Rong Yu ◽  
Lin Su ◽  
Yidong Fang ◽  
...  
Keyword(s):  
Heat Pump ◽  
Electric Vehicles ◽  
Flow Characteristics ◽  
Cold Climate ◽  
Positive Temperature ◽  
Pump System ◽  
Cooling Performance ◽  
Heat Pump System ◽  
Heating Performance ◽  
Driving Range

Abstract Utilizing the heat from air source with heat pump system in electric vehicles shows a significant advantage from thermoelectric heat source for heat supply in cold climate. It could improve the driving range of electric vehicles considerably in winter and replace the positive temperature coefficient (PTC) heater with an acceptable cost and reliability. In this work, a newly designed heat pump system was first introduced with less components and cost. Second, experiments were conducted to investigate its cooling performance, and subsequent heating performance from −10 to 10 °C. The typical heat transfer and flow characteristics of refrigerant were recorded, and the behavior of each component including compressor, evaporator, condenser, and outside heat exchanger were analyzed and interpreted. The results showed that the heating and cooling performance of the new heat pump system could almost remain the same with traditional air-conditioning system in automobile and surely satisfy with the heat requirement of electric vehicles. In the heating mode, the maximum heating capacity increases by 13% at 400 m3/h air volume from 300 m3/h at the ambient temperature −10 °C, while the outlet air temperature decreases by 4–6%. In addition, using a heat pump system showed an increase in the driving range of electric vehicles by 25–31% as compared to PTC heaters.

Numerical Simulations of a Ground Source Heat Pump System With Pile Heat Exchangers

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
Masahito Oguma ◽  
Takeshi Matsumoto ◽  
Takao Kakizaki
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Heat Supply ◽  
Ground Surface ◽  
Ground Source Heat Pump ◽  
Pump System ◽  
Heat Pump System ◽  
Ground Source

Feasibility of a ground source heat pump (GSHP) system with pile heat exchangers for use in houses is evaluated through a numerical simulation. This GSHP system differs from ordinary borehole-type GSHP systems because short foundation piles installed at close intervals are used as heat exchangers. It is shown that the annual heat supply provided by this GSHP system is able to satisfy the demand of a house due to the air-source exchange at ground surface.

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