Studies On The Performance Of The Composite Heat Pump Water Heater Based On Micro-channel Collector

Solar-air compound source heating pump water heater based on micro-channelcollector is a heat pump system which adopt micro-channel collector as its auxiliaryevaporator and collector. The composite heat pump system merged solar thermaltechnology and heat pump technology. In this system solar energy can be directly useto heat water, or be use as assisted evaporation heat for evaporator. The system cancompensate for the lack of air-source heat pump and solar water heater. Thetechnology can alleviate the problem of large energy consumption in electric waterheater and low energy efficiency in gas water heater. It advance building energyrationality and strengthen energy efficiency with obvious environmental andeconomic benefits.The composite heat pump system with ingenious structural design can use solarand air heat maximally to achieve operating under a variety of working conditionsaccording to the climatic conditions and effective control system. And themicro-channel collector in this paper is the key components to achieve complexsystems using solar energy and air heat. In order to verify the feasibility ofmicro-channel in composite heat pump system, we conducted a micro-channelcollector modeling for simulation. Results verify that the application of micro-channelcollector in the composite system is feasible by comparing the average platetemperature, heating time, collector efficiency and other simulation data of traditionalflat-plate collectors. The collector efficiency of micro-channel heat collector is9.3%higher than the traditional flat-plate collector with the best tube center distance，andit’s20.6%、30.6%higher than the commonly used two flat-plate collectors. Theresults verified the feasibility of micro-channel collector application in the compositeheat pump system.In order to study the performance of the composite heat pump，we establishedmathematical models of condenser, evaporator and micro-channel collector withdistributed parameter, compressor model with lumped parameter and thermalexpansion valve with chart. We set average seasonal environmental parameters ofChangsha as the four season conditions and established balance constraints, boundaryconditions, algorithms of system simulation and components to achieve the solutionof the whole system model equations. In this paper, Matlab language was used to write simulation program of the system and simulate system performance.The simulation work was divided into two parts. Firstly, we analyzed the effectof ambient temperature, solar light intensity to the evaporation temperature and COPvalue of the system. Micro-channel collector in system can improve the evaporationtemperature and the COP value from simulation. This feature is very advantageous toreduce the defrost energy consumption in winter conditions. Simultaneously, we havestudied the system operating performance of four seasons in Changsha and analyzedthe water temperature, evaporation temperature and COP values in the relationshipwith the heating time under different climatic conditions. Comparing with seasonalenergy consumption of electric water heater and air heat pump water heater, theenergy efficiency of composite heat pump is higher than traditional air heat pumpwater heater and electric water heater. The composite heat pump water heater in thispaper saved25.4%energy than traditional air heater, and saved71.7%energy thantraditional air heater electric water heater per year. The results provided a reliabletheoretical basis for physical experiments and applications of solar-air compoundsource heating pump water heater based on micro-channel collector.