Steady state behavior of a booster heat pump for hot water supply in ultra-low temperature district heating network

Employing booster heat pumps (BHP) in district heating systems can provide a way to use low temperature heat sources for district heating as they allow locally increasing the water temperature on the user side where necessary. Thereby, it can provide decreased heat loss of a district heating system. This experimental study investigated steady state thermal behavior of a BHP for cases with different forward temperature and different flow rates on the user side. The unit used R134a as working fluid. The results revealed that the Coefficient of Performance (COP) of the BHP system has an optimal value at the studied range. At a forward temperature of 45 degrees C the heat pump reached maximum COP of 4.95, heating capacity of 15.36 kW, and exergy efficiency of 33.4 %, respectively. Lorenz COP and Lorenz efficiency is ranged from 13 to 27 and 0.16 to 0.26, respectively. Exergy destruction of each component as well as exergy efficiency of BHP used in the proposed system have also been analyzed, which showed that the compressor take the highest the exergy destruction among the components. The exergy efficiency ranged from 24.9% to 33.4% in the considered conditions. The share of exergy destruction of condenser and evaporator were influenced by the heat transfer condition on both sides, which reveals that the BHP can achieve potential performance improvement by better matching heat transfer profile of condenser and evaporator. (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

The study investigated the steady state thermal behavior of a booster heat pump (BHP) under different forward temperatures and flow rates, revealing that the BHP reached maximum COP of 4.95, heating capacity of 15.36 kW, and exergy efficiency of 33.4% at a forward temperature of 45 degrees Celsius. The compressor was found to have the highest exergy destruction among the components.