Papers by Keyword: Coefficient of Performance (COP)

Abstract: This paper proposes a simplified theoretical model of Pulsating Heat Pipe (PHP) employed in a vapour compression refrigeration system. The model developed is mainly based on well known physical equations and partially based on empirical correlation. The present theoretical investigation of PHP is focused to explore its suitability as a heat exchanger in the condenser of vapour compression refrigeration system. A parametric analysis is carried out to design the vapour compression refrigeration system with PHP as the condenser. The performance of the system is evaluated for different PHP diameters, working fluids, evaporator and condenser temperatures and evaporator and condenser lengths. The effect of super heating and sub cooling the refrigerant are also studied. The results showed an increase in performance of the system at higher evaporator and lower condenser temperatures. The best results are obtained with R-12 as the working fluid. Also there is an increase in the COP of the system due to decrease in pressure drop in the condenser.

Abstract: This study presented the energy performance evaluation of a ground-water heat pump (GWHP) system based on actual operational data. The GWHP system was installed for apartment buildings in Wuhan, China. During one year, various operating parameters of the GWHP system were monitored and the coefficient of performance (COP) of system was determined based on the measurement. The energy consumption of the GWHP system is more than twice the average value of split air conditioner on residential application, because of continuously operating of the GWHP system and frugally intermittence operating of split air conditioner. The GWHP system is more economical than other central system. The energy savings rate of the GWHP system was 41.5% for the heating season comparing with boiler and 42% for the cooling season comparing with air source heat pump.

Abstract: Heat recovery of low pressure steam in steam condenser of thermal power plant was attractive because of its great economy and environmental value. This paper reported the experimental investigation results on the application of a heat pump water heater (HPWH) using low pressure steam in steam condenser as heat source. The working principles and features of the prototype heat pump were introduced. The effects of various parameters, including water flow rate and inlet temperature of heat pump condenser were investigated. Influence of vacuum pump on HPWH was also discussed. Results show that performance of HPWH is governed strongly by the change of water flow rate and inlet water temperature of heat pump condenser and vacuum pump. Maximum outlet water temperature of the test HPWH is 65°C and the maximum coefficient of performance (COP) is 4.5.

Abstract: This paper presents a numerical approach for determining the motive nozzle and constant-area of an ejector as an expansion device, based on cooling capacity of the split-type air conditioner using R22 as working fluid. The use of an ejector as an expansion device in split-type air conditioner can enhance the coefficient of performance (COP) system. Typically, the split-type air conditioner may be installed on the geographical area with moderate or high outdoor air temperature using capillary tube. For this reason, the motive nozzle and constant-area diameters of the ejector must be designed according to these conditions. The diameters of the ejector are crucial in improving the COP. The results showed that the motive nozzle diameter is constant (1.14 mm) with variations of the condenser temperature, whereas the constant-area diameter decreases as the condenser temperature increases.

Abstract: To predict the working performance of the jet refrigeration system more precisely, including the condensing temperature and coefficients of performance, this paper presents a 1-D analysis model with the varying specific heat ratio. During the evaluation, the working process of the constant pressure ejector is divided into three sections with different specific heat ratios. By comparing the results from Eames experiment, the simulation results indicate that this model is more reasonable, and the error of the simulation is within 20%, which is significantly smaller than the error of Eames model at 40%.

Abstract: A grey box model of screw ground source heat pump unit has been established and operating characteristics of the unit using R22 refrigerants were simulated. The effects on refrigerating capacity, heating capacity, power consumption of the compressor and COP on conditions of cooling and heating have been analyzed with different inlet water temperature of evaporator and inlet water temperature of condenser. Results show that main factor which affecting COP of heat pump unit is inlet water temperature of condenser. The change of refrigerating capacity and heating capacity are mainly caused by inlet water temperature of evaporator. Measures can be done to decrease the inlet water temperature of condenser when the unit operates for a long time and to increase inlet water temperature of evaporator on very hot or very cold conditions.

Abstract: According to the energy-consuming characteristics of buildings in hot summer and warm winter area, a direct-expansion solar-ground source heat pump system is put forward. This system runs the direct-expansion solar heat pump system in summer and direct-expansion solar-ground source heat pump system in transition season and winter to produce hot water. The article analyses the thermal contribution rates of double-heat sources of the system under various working conditions in different seasons. Results indicate that the total area of solar evaporators matches the power of units and the matching value is 2.18m²/kW. When the average daily total solar radiation is 15.8MJ/m² in summer, 11.2MJ/m² in transition season and 11.2MJ/m² in winter, the unit area heat transfer are respectively about 1.48kW/m², 1.1kW/ m² and 0.43kW/m². The annual solar thermal contribution rate is 46.4% and the annual soil thermal contribution rate is 32%, which can reduce 57.96% quantity of heat absorbing from the soil.

Abstract: In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. It is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending up on the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%.

Abstract: A solar assisted air source heat pump unit is designed. The mathematical model of the unit is established and two hybrid operating conditions of the system are simulated. The simulative studying results shows that in winter the solar assisted air source heat pump unit can make full use of solar energy and the coefficient of performance (COP) of air source heat pump can be improved. In summer the cooling heat of air source heat pump could be recovered to improve the stability of solar hot water collector and the COP of the air source heat pump unit is greatly improved. The performance of solar assisted air source heat pump unit is better than that of with no solar assisted air source heat pump.

Abstract: It is the new way of the thermal power plant energy conservation to recycling plant circulating water waste heat for heating with the heat pump technology. The recovery of low temperature waste heat is the background. And lithium bromide absorption heat pump is the object of this study. The impact of changes in temperature parameters on the performance of heat pump unit is analyzed. As a theoretical basis for the design of the heat pump system and power plant heat pump unit’s optimal operation provide a reference. The result provides a theoretical reference for the optimal operation of the heat pump system design and power plant heat pump units.