Mapping of Coefficient of Performance for large-scale ammonia heat pumps for district heating systems
Abstract
Many system configurations of large-scale heat pumps (HP) are applicable to a district heating system, and choosing the right HP technology may be a challenge. In this study, thermodynamic models of eight different HP configurations are used to compare the Coefficient of Performance (COP) and Lorenz efficiency, for a range of sink and source outlet temperatures. Furthermore, for a specific case the total volume flow rate for each configuration was compared. The results revealed that a configuration with two two-stage cycles with low stage desuperheat heat exchangers in most operating conditions was superior in terms of COP. However, for all considered operating conditions at least three configurations obtained a COP which was less than 3 % lower than the best one. Comparing the volume flow rates among the configurations a combination of a one-stage cycle and a two-stage cycle with low stage desuperheat heat exchanger holds the lowest needed volume flow rate.