An Experimental Thermal Performance Analysis & Comparison of a Direct Expansion Solar Assisted Heat Pump Water Heater With Unglazed and Single Glazed Collector

An experimental thermal performance analysis of a direct expansion solar assisted heat pump for domestic water heating is presented. This system uses flat plate collector as an evaporator with a surface area of 2.23m 2 , a small R134a reciprocating-type compressor with rated input power 245 W, an insulated hot water tank having a volume of 30L and capillary expansion tube having a bore of 0.036". For water heating the energy sources are mostly liquefied petroleum gas and electricity. The use of heat pump or solar water heating, particularly the solar-assisted heat pump options, is not popular. In this paper, the potential application of direct-expansion solar-assisted heat pump (DE- SAHP) system was examined. Experimental studies measure the solar intensity, water inlet temperature, water outlet temperature, ambient temperature, time step, and heat gain at the condenser for finding out the coefficient of performance, also a performance comparison between glazed and unglazed collector was done. The COP for the DE-SAHP built in the present study lies in the range 3-7 depending on operating conditions. Hot water and steam form an integral part of various industrial and commercial applications and with rising oil prices, there has never been a better time to look at heating water by harnessing energy from the sun. Hot water can be used in number of applications such as large scale hot water usage for bathing and laundry applications in hostels, hospitals and high rise apartment buildings, pre feed for boilers for steam generation, for various industrial applications, milk dairies for applications such as pasteurization, condensation, cleaning, leather processing industry for drying and tanning. Hot water also used in metal finishing industry for degreasing and phosphating, resin emulsification in polymer industry, drying and related processes in pharmaceutical industry, solar drying through air heating is an area of growing interest and swimming pool heating is a popular concept in India and abroad. In the direct expansion solar assisted heat pump water heater (direct SAHP) system, the solar collector serves as an evaporator where the refrigerant absorbs the incident solar energy and energy rejected by the condenser contributes to water heating. Since the solar collection system can supply energy at temperatures higher than the ambient outdoor air, the capacity and coefficient of performance improves. In virtue of its above mentioned advantages, the direct SAHP is expected to have a huge potential market in daily life. In the direct SAHP, condenser can be arranged as an external heat exchanger supplying a hot water or arranged as an immersed coil in the hot water storage tank. The main advantage of direct SAHP as compared to SAHP is the better thermal performance due to direct expansion and evaporation of the refrigerant in the collector. In direct SAHP, long supply and return lines are required between roof mounted solar collector and the thermal storage located in the heated interior of the building. As these lines are charged with refrigerant and require specialized mechanics, this makes the installation difficult. The study however concluded that this system configuration offered significant performance and cost benefits over the solar assisted heat pump water heater. In this paper, we will discuss and compare the performance of direct expansion solar assisted heat pump with and without glazing.