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.

Modeling of Surge Characteristics in Turbo Heat Pumps

2010 ◽  
Author(s):  
Hye Rim Kim ◽  
Seung Jin Song
Keyword(s):  
Gas Turbine ◽  
Heat Pump ◽  
Heat Pumps ◽  
Ideal Gas ◽  
Working Fluid ◽  
Pump System ◽  
Turbine Engine ◽  
Heat Pump System ◽  
Expansion Valve ◽  
Two Phases

This paper presents a new analytical model of surge dynamics in turbo heat pumps. Turbo heat pumps use refrigerants as the working fluid and consist of a centrifugal compressor, condenser, expansion valve, and evaporator. Compared to a gas turbine engine, the turbo heat pump system introduces additional complexities. First, the turbo heat pump forms a closed-loop system. Second, the system has two plenums — condenser and evaporator — which are coupled to each other. Third, the heat pump runs on a refrigeration cycle with two phases — vapor and liquid. Fourth, heat transfer effects of evaporation and condensation have to be considered. Fifth, unlike air, a refrigerant has strong real gas effects and thus cannot be modeled as an ideal gas. The new model addresses such additional complexities on the basis of the first principles of conservation of mass, momentum, and energy. When applied to a gas turbine system, the new model’s predictions become identical to those from the Greitzer’s model. Furthermore, comparison with the available experimental data shows that the model can also accurately predict surge behavior in actual turbo heat pumps. Finally, the effects of Greitzer’s B parameter and the ratio of evaporator and condenser volume have been examined. Parameter B influences both surge shape and frequency. Finally, surge frequency is extremely sensitive to the ratio of the two plenum volumes.

Modeling of Surge Characteristics in Turbo Heat Pumps

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Hye Rim Kim ◽  
Seung Jin Song
Keyword(s):  
Gas Turbine ◽  
Heat Pump ◽  
Heat Pumps ◽  
Ideal Gas ◽  
Working Fluid ◽  
Pump System ◽  
Turbine Engine ◽  
Heat Pump System ◽  
Expansion Valve ◽  
Two Phases

This paper presents a new analytical model of surge dynamics in turbo heat pumps. Turbo heat pumps use refrigerants as the working fluid and consist of a centrifugal compressor, condenser, expansion valve, and evaporator. Compared with a gas turbine engine, the turbo heat pump system introduces additional complexities. First, the turbo heat pump forms a closed-loop system. Second, the system has two plenums, condenser and evaporator, which are coupled to each other. Third, the heat pump runs on a refrigeration cycle with two phases: vapor and liquid. Fourth, heat transfer effects of evaporation and condensation have to be considered. Fifth, unlike air, a refrigerant has strong real gas effects and thus cannot be modeled as an ideal gas. The new model addresses such additional complexities on the basis of the first principles of conservation of mass, momentum, and energy. When applied to a gas turbine system, the new model’s predictions become identical to those from the Greitzer’s model. Furthermore, comparison with the available experimental data shows that the model can also accurately predict surge behavior in actual turbo heat pumps. Finally, the effects of Greitzer’s B parameter and the ratio of evaporator and condenser volume have been examined. Parameter B influences both surge shape and frequency. Finally, surge frequency is extremely sensitive to the ratio of the two plenum volumes.

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.

Thermoeconomic Analysis on the Performance Characteristics of a Multi-Stage Irreversible Combined Heat Pump System

2000 ◽  
Vol 122 (4) ◽  
pp. 212-216 ◽  
Author(s):  
Jincan Chen ◽  
Chih Wu
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Power Input ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Pump System ◽  
Heat Pump System ◽  
Maximum Profit ◽  
Multi Stage

A cycle model of a multi-stage combined heat pump system, which includes the irreversibility of finite rate heat transfer across finite temperature differences and the irreversibilities inside the working fluid, is established and used to investigate the influence of these irreversibilities on the performance of the system. The profit of operating the heat pump system is taken as an objective function for optimization. The maximum profit is calculated for a given total heat transfer area or total thermal conductance of heat exchangers. The coefficient of performance, heating load, and power input at the maximum profit are determined. The distribution of the heat transfer areas or the thermal conductances of heat exchangers and the temperature ratios of the working fluids of two adjacent cycles in heat exchange processes are optimized. The results obtained here are generally significant. They are suitable for an arbitrary-stage irreversible and endo- reversible combined heat pump system. [S0195-0738(00)01104-3]

Refrigerant Subcooling Correlations for Different Expansion Devices for a Non-Intrusive Charge Indicator

2006 ◽  
Author(s):  
Z. Gao ◽  
V. C. Mei
Keyword(s):  
Heat Pump ◽  
Low Cost ◽  
Heat Pumps ◽  
Air Conditioner ◽  
Cooling Mode ◽  
Pump System ◽  
Air Conditioners ◽  
Heat Pump System ◽  
Heating And Cooling ◽  
Expansion Valve

The most common problems affecting residential and light commercial heating, ventilation, and air-conditioning (HVAC) systems are slow refrigerant leaks. Equipment users are usually not aware of the problem until most of the refrigerant has escaped. A low-cost, non-intrusive refrigerant charge indicator has been developed, based on temperature measurements and correlations formed to interpret the measured temperatures. It can be used to provide real time warnings to the equipment users before the majority of refrigerant is escaped. It could be inexpensive and easy to incorporate into existing heat pumps and air conditioners. Extensive laboratory experimental work was performed on a 2-ton window air conditioner and on a 2.5 ton split heat pump system. It was found that the heat pump was not sensitive to slow refrigerant leak because of the long liquid line. Liquid subcooling was measured to determine the system charge status before a substantial amount of refrigerant was leaked. This study reports the finding of correlations formed for liquid subcooling for the orifice plate and thermal expansion valve used on the heat pump system for both heating and cooling mode operation.

DETERMINING THE PROFITABILITY OF GREENHOUSE ELECTROTECHNOLOGIES: A MODELING APPROACH

HortScience ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 249a-249
Author(s):  
Eric A. Lavoie ◽  
Damien de Halleux ◽  
André Gosselin ◽  
Jean-Claude Dufour
Keyword(s):  
Energy Consumption ◽  
Heat Pump ◽  
Water System ◽  
Heat Pumps ◽  
Hot Water ◽  
Pump System ◽  
Heat Pump System ◽  
Artificial Lighting ◽  
Hot Air ◽  
Marketable Fruit

The main objective of this research was to produce a simulated model that permitted the evaluation of operating costs of commercial greenhouse tomato growers with respect to heating methods (hot air, hot water, radiant and heat pumps) and the use of artificial lighting for 1991 and 1992. This research showed that the main factors that negatively influence profitability were energy consumption during cold periods and the price of tomatoes during the summer season. The conventional hot water system consumed less energy than the heat pump system and produced marketable fruit yields similar to those from the heat pump system. The hot water system was generally more profitable in regards to energy consumption and productivity. Moreover, investment costs were less; therefore, this system gives best overall financial savings. As for radiant and hot air systems, their overall financial status falls between that of the hot water system and the heat pump. The radiant system proved to be more energy efficient that the hot air system, but the latter produced a higher marketable fruit yield over the 2-year study.

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.

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