Waste heat recovery of air conditioning on thermal efficiency enhancement of water heater

Abstract

Air conditioning units are used to deliver comfortable air in households for the daily life of humans. This generates waste heat into the surroundings, that can cause global warming. This study investigated the thermal performance of water heaters recovering waste heat from air conditioners. A double-tube heat exchanger was installed between the compressor and the condenser to recover heat from the air conditioner. The inlet water temperature ranges from 15 °C to 40 °C, mass flow rates range from 2.5 L/m – 12.5 L/m, and water heater power input of 880 W – 3520 W is investigated. The results showed that water heaters have high thermal efficiency at low water mass flow rates. The waste heat of the air conditioner was recovered, which increased the thermal efficiency of the water heater by 12 % – 180 %, higher than the conventional type by approximately 50 %. The inlet water temperature ranges from 15 °C to 25 °C, and the input power range from 880 W to 1760 W has a significant impact on the thermal efficiency of the water heater. The energy consumption of the air conditioner decreased significantly when it was integrated with the heat recovery system. In addition, the water mass flow rate affected the energy consumption of the air conditioner. This study provides guidelines for improving the thermal efficiency of water heaters to reduce carbon dioxide emissions and heat rejection from air conditioners, leading to a reduction in global warming.