| In this paper, a solar assisted multi-functional heat pump is proposed based on a detailed solar heat pump survey, which has integrated household heat pump air conditioner with solar hot water heater. On the basic functions of retaining the original summer cooling, air source heat pump heating in winter, heat pump water heater throughout the year and solar hot water heating modes, it has added summer cooling integrated water heater and solar hot water auxiliary water source heat pump heating function in winter. The new functions has achieved recycling of waste heat, reduced thermal pollution, and mitigated the problem of outdoor coil frost in air source heat pump mode.This paper describes the operating principle and the realization of each mode of the proposed system. The experimental prototype has been established in accordance with the schematic design of the refrigerant circulation. The paper studied five operation modes like summer cooling, cooling and water heating, air source heat pump system in winter, solar hot water assisted water source heat pump and heat pump water heater around the year. Furthermore, it has provided a detailed analysis of the operation performance. The results show that the system performs well under the corresponding experimental conditions. Here are the main conclusions obtained:1. During the summer cooling experiment, when the compressor's suction temperature is 10.0℃and exhaust temperature is 79.0℃, the system has a smooth working state with the average cooling capacity is 3803w and the average COP is 3.1;2. A detailed summer cooling integrated water heating mode experimental study has been carried out. Its results show that when the outdoor fan is turned off, the water heating rate is faster and the average cooling capacity is 2900w; after the fan is turned on, the system cooling capacity increases rapidly to the maximum value 3700w, the average cooling capacity is 3500w, and the average cooling COP is 3.0, while the heat storage tank water temperature increases very slowly, the hot water temperature changes from 45℃to 55℃within 280 min. During the whole operation process, when the outdoor fan is turned off, the integrated system COP value is over 5.0; after the fan is turned on, the value is still higher than 3.0;3. The system operates stably during the air source heat pump heating mode. With the high exhaust temperature, the system can release more heat to the room to meet the indoor heat load, whose the average heat capacity is 3750w, and during the experimental period, the system′s average heating COP value is 3.4;4. The tests of solar assisted heat pump heating function show that the system heating COP is over 4.0, when the water temperature is between 30℃and 40℃, which is higher than air source heat pump. With water temperature drops in the water tank, the system COP value still has advantages. However, the decline of the compressor temperature has caused the heating effect decreased;5. The performance analysis of multi-function solar assisted heat pump water heating mode shows that: with the ambient temperature increasing, the suction and discharge pressure of the system have been increased. Under comparatively higher ambient temperature, the system is still working within safe limits. System performance is closely influenced by the environment: when the environment temperature is 19.4℃, the hot water heating time is visibly shorter, the coefficient of performance heightens greatly, and the hot water heating time is 58 min shorter than the value when the environmental temperature is 6.7℃.Finally, the article analyzed the phenomena of lacking of refrigerant and the high suction superheat during the experiment. Based on the original schematic diagram, an improved program has been proposed, which has increased two solenoid valves and a capillary tube throttle to solve the above phenomena that may occur. What's more, the control method about summer cooling integrated water heating mode and winter solar assisted heat pump heating mode are also introduced. |
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