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The present investigation deals with the performance assessment of Cascade heat pump plants. The overall power consumption for a Cascade system for typical heat pump characteristics was studied. Four environment friendly refrigerant pairs R717/R134a, R410A/R134a, R407C/R134a, and R717/R600a were investigated at low temperature cycle (LT) evaporator...
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Many types of heat pumps raise energy from a lower source to a high-temperature environment. These could be classified as a single, multistage compression, or a cascade system. This report aims to find the most suitable technique for using seawater as a heat source. The discharge hot water temperature from the heat pump is required at (65 to 70) °C...
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Citations
... Soltani et al. [15] compared the performance of single stage and hydronic cascade heat pumps for generating hot water. Tarrad [16] examined a methodology to generate hot water in a cascade heat pump using low temperature heat source. Qu et al. [17] proposed a control algorithm for an air source cascade heat pump used for hot water generation. ...
The use of cascade heat pumps for hot water generation has gained much attention in recent times. The big question that has attracted much research interest is how to enhance the performance and energy saving potential of these cascade heat pumps. This study therefore proposed a new cycle to enhance performance of the cascade heat pump by adopting an auxiliary heat exchanger (AHX) in desuperheater, heater and parallel positions at the low stage (LS) side. The new cascade cycle with AHX in desuperheater position was found to have better performance than that with AHX at heater and parallel positions. Compared to the conventional cycle, heating capacity and coefficient of performance (COP) of the new cascade cycle with AHX in desuperheater position increased up to 7.4% and 14.9% respectively.
... References [3][4][5][6][7][8] investigated the performance of cascade heat pump circulating pairs of environment friendly refrigerants when extracting the energy from seawater at low temperature for heating purposes. He studied a variety of issues in regards of the implementation of those systems such as evaporator temperature, intermediate temperature of cascade heat exchange, condensing temperature, CO 2 emission and the economic feasibility of such energy sources. ...
This investigation focuses on the renewable geothermal energy source utilized as a reservoir for a water chiller unit in the cooling mode. Two hydrocarbon refrigerants, R290 and R600a were suggested to be implemented in a closed loop system to produce chilled water for air conditioning purposes. The traditional R-22 and its substitute R410A were also investigated in a direct expansion geothermal system. The analysis was carried out at the evaporation and condensation temperature ranges of (-25 to -5) °C and (15 to 35) °C respectively. The data showed that R-290 revealed similar coefficient of performance as that of R-22. R-410A exhibited a lower coefficient of performance than that of the R-22 refrigerant by (1-5) %. On the contrary, R-600a showed a higher coefficient of performance than that of the R-22 by about (3) % for the investigation range of operating conditions. R-410A refrigerant exhibited the highest load in comparison with R-22 among other circulated refrigerants by (1.5) %. R-600a showed a lower condenser load than that of the R-22 system by a negligible margin value. The hydrocarbon refrigerants and the azeotrop mixture were found to be proper candidates to replace R-22 in geothermal system.
... The heat pump extracts energy from the low temperature source through a thermal fluid such as (30) % ethylene glycol -water or (20) % propylene glycol-water mixtures. This thermal fluid heat carrier is selected according to the low temperature energy source, Tarrad [27][28][29][30]. A (43) kW heat pump may be implemented to extract energy from a sea water through the ethylene glycol-water solution to meet the heating load demand at highest investigated wind speed of (5) m/s. ...
The transient temperature dependency and heating load requirements were assessed for a hypothetical swimming pool size of (100) m3 prepared at a temperature of (28) °C. The pool first preparation stage occupied quite a long running time of heat pump to raise the pool water from initial temperature of (12) °C prior to its usage. Wind speed lied in the range of (1.8-18) km/h and air temperatures of (15 and 20) °C at (50) % relative humidity. The analysis showed that the evaporation heat loss was within the range of (54-69) % depending on the wind speed. The surface convection loss occupied the range of (15-21) % at (1.8-18) km/h wind speed range. It was followed by the radiation component of (7-21) % and the lowest was the convection-conduction component of (3-8) % range through the pool walls. Correlations for the design heat load, surface evaporation rate and heating up temperature of the pool in terms of the wind speed and time were accomplished. The heating load is either extracted from a ground or sea water for maintaining the thermal aspects of the pool. This heat source was integrated with the swimming pool for the purpose of water temperature control.
The economical and clean environment issues for a sustainable energy source at low temperature (LT) were considered and compared to natural gas technology as a fossil fuel source. The friendly environment refrigerants R410A, R407C, R717, R134a, and R600a were analyzed in an approximately 500 kW heating load output cascade heat pump. The heat pump was investigated at an intermediate temperature of 35 ° C, high temperature (HT) cycle condenser at 70 ° C, and compressors isentropic efficiency of 70%. All analyzed refrigerant pairs exhibited high heating season performance factor (HSPF), and it was ranged between 7 and 8.5. The thermal performance comparison revealed that the HSPF for R717/R600a showed the highest values among other refrigerant pairs. The results showed that at LT cycle evaporator temperature range of -10 to -2 ° C, the natural gas technology revealed a higher season heating cost values than that of the heat pump plant by up to 10%. On the contrary at lower LT evaporator temperature, the heat pump plant technology exhibited a higher season heating cost lied in the range of 4-13.6% than that of the natural gas system. At compressors isentropic efficiency of 90%, the seasonal heating cost of the heat pump plant was lower than that of the natural gas technology by the range of 9-25% at test conditions. The mean seasonal CO2 amount released by the natural gas firing technology from all tested refrigerant pairs ranged between 2.1 and 2.5 times that of the heat pump plant technology for the investigated LT evaporator temperature range.
