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.

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.

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.

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 Numerical evaluation of the performance of a single-well groundwater source heat pump system in Beijing, China

2019 ◽  
Vol 38 (1) ◽  
pp. 201-221 ◽  
Author(s):  
Tianfu Xu ◽  
Fengyu Li ◽  
Bo Feng ◽  
Guanhong Feng ◽  
Zhenjiao Jiang
Keyword(s):  
Heat Transport ◽  
Heat Pump ◽  
Transport Model ◽  
Heat Pumps ◽  
Transport Processes ◽  
Pump System ◽  
Heat Pump System ◽  
Single Well ◽  
Groundwater Source ◽  
Beijing China

Shallow geothermal energy is stable and clean. Using a heat pump to produce groundwater and realize heating and cooling can effectively prevent haze and reduce energy consumption. To reduce engineering costs, many buildings in Beijing, China, plan to utilize single-well groundwater source heat pumps. Numerical modeling is an effective way to gain an understanding of thermal transport processes. However, wellbore-reservoir coupling and the uncertainty of productivity due to geological parameters make simulation difficult. A wellbore-reservoir-integrated fluid and heat transport model is defined by T2Well simulator to predict the productivity of a typical single-well system, with consideration of complex geological factors. The model is validated by the analytical model developed in Beijing, China. The fluid processes in the wellbore are described by 1 D non-Darcy flow, and the reservoir 3 D fluid and heat transport processes are calculated. Six crucial factors satisfying a random distribution are used, and for a single well that can supply heat for an area of 9000 m2, the output temperature during the heating season ranges from 11°C to 15°C.

An Economical Analysis on a Solar Greenhouse Integrated Solar Assisted Geothermal Heat Pump System

2005 ◽  
Vol 128 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Onder Ozgener ◽  
Arif Hepbasli
Keyword(s):  
Heat Pump ◽  
Cooling System ◽  
Heat Pumps ◽  
Renewable Energy Resources ◽  
Ahp Method ◽  
Geothermal Heat ◽  
Pump System ◽  
Heat Pump System ◽  
Economical Analysis ◽  
Geothermal Heat Pump

The main objective in doing the present study is twofold, namely (i) to review briefly the utilization of geothermally heated greenhouses and geothermal heat pumps in Turkey, since the system studied utilizes both renewable energy resources and (ii) to present the Analytical Hierarchy Process (AHP) as a potential decision making method for use in a greenhouse integrated solar assisted geothermal heat pump system (GISAGHPS), which was installed in the Solar Energy Institute of Ege University, Izmir, Turkey. This investigation may also be regarded as the one of the limited studies on the application of the AHP method to GISAGHPs, as no studies on the GISAGHPS have appeared in the literature. In this context, an economic analysis is performed based on the life cycle costing technique first. The results are then evaluated by applying the AHP method to a study, which is a comparative study on the GISAGHPS and split system. The results indicated that the GISAGHPS is economically preferable to the conventional split heating/cooling system under Turkey’s conditions.

Optimization of Working Ground Heat Storage With Seasonal Regeneration

2006 ◽  
Author(s):  
Pawel Olszewski
Keyword(s):  
Energy Storage ◽  
Heat Exchange ◽  
Heat Pump ◽  
Input Data ◽  
Heat Storage ◽  
Target Function ◽  
Working Fluid ◽  
Solar Collectors ◽  
Pump System ◽  
Heat Pump System

The aim of the research was an optimization of long-term heat storage with seasonal regeneration. Energy consumption for central heating during wintertime, transfererred from ground energy storage using a heat exchange device, is the operating principle of such systems. Warmed working fluid is then used in a heat pump system. However, more accurate calculations showed that over time of usage, there is a trend toward cooling at deeper round layers. Such a situation leads to a lowering of ground potential when using heat pump systems. A possible solution to this problem is the application of summer regeneration: during summer months, the working fluid is firstly warmed in solar collectors, and then forced into the same boreholes. The numerical model of a vertical, ground heat exchange device (configured as a "pipe in pipe", known as a Fields' pipe) was specially developed. Temperature distribution of the working fluid along the pipe was one of the boundary conditions, for the co-axial, time-variable, heat conduction task, which described the heat flow in energy storage. The numerical simulation of solar collectors work was based on the Hottel - Whillier - Bliss equation, in which energy flow from the solar collector is calculated, dependant on external parameters such as: insulation or ambience temperature. The combination of three computational parts- the ground heat exchange device, energy storage area and solar collectors battery- allows the target function to be defined for task optimization. The subject of optimization was an energy quantity, which can be taken from energy underground storage, and then utilized by the heat pump system. In the summarized paper, a combination of the input data, which influenced the efficiency of energy storage, was chosen. Hypothetical data were: outside diameter and length of heat exchange device, distance between pipes, fluid flow through the pipe during charge and discharge processes or temperature of inlet working fluid. The influence of individual parameters on the target function, holding all input data constant, was analyzed. A developed evolutionary numerical code known as GENOCOP I (GEnetic algorithm for Numerical Optimization for COnstrained Problems) [3] was used for optimization. After preliminary correction of boundary values of the input data, nine attempts of optimization were taken up. The research results identified optimal values of input parameters for which maximum energy could be taken from ground storage.

Modelling of an Indirect Solar-Assisted Heat Pump System for a High Performance Residential House

2013 ◽  
Author(s):  
Jenny Chu ◽  
Cynthia A. Cruickshank ◽  
Wilkie Choi ◽  
Stephen J. Harrison
Keyword(s):  
Heat Pump ◽  
High Performance ◽  
Simulation Software ◽  
Hot Water ◽  
Solar Thermal ◽  
Working Fluid ◽  
Space Heating ◽  
Pump System ◽  
Heat Pump System ◽  
Solar Thermal Collectors

Heat pumps are commonly used for residential space-heating and cooling. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario’s efforts to develop a high performance house for the 2013 DOE Solar Decathlon Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system is designed to provide domestic hot water, space-heating, space-cooling and dehumidification. The system included a cold and a hot thermal storage tank and a heat pump to move energy from the low temperature reservoir, to the hot. The solar thermal collectors supplies heat to the cold storage and operate at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building’s energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing and configuration of the system. This paper provides an overview of the model and summarizes the results of the study. The simulation results suggested that the investigated system can achieve a free energy ratio of about 0.583 for a high performance house designed for the Ottawa climate.

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