Charge degradation, undercharging, LCCP, correlation
All the vapor compression systems continuously leak part of the refrigerant charge to the environment, whether during operation or servicing. As a result of the slow leak rates during operation, the refrigerant charge decreases until the system is serviced. This charge degradation, after certain limit, starts to have detrimental effect on the system’s capacity, power consumption, and coefficient of performance (COP). This paper presents a literature review and a summary of the previous experimental work on the under charging or charge degradation of different vapor compression systems especially the ones without a receiver. These systems include residential air conditioning and heat pump systems utilizing different components and refrigerants, and water chiller systems. It is shown that most of these studies show similar trends for the effect of the charge degradation on the system performance. However, it is found that although much of the experimental work exist on the effect of charge degradation on the system performance, no correlation, or comparison yet exists. Thus, based on the literature review, four different correlations, that characterize the effect of charge on system capacity and power consumption, are developed for different systems as follows: two for air-conditioning systems, one for vapor compression water-to-water chiller systems, and one for heat pumps. These correlations can be implemented in vapor compression cycle simulation tools to obtain a better prediction of the system performance throughout its lifetime. The correlations are then implemented in an open source tool for life cycle climate performance (LCCP) based design of vapor compression systems. The LCCP of a residential air conditioning system is evaluated using the tool and the effect of charge degradation on the results is studied. The air conditioning system is simulated using a validated component-based vapor compression system model. The LCCP results obtained using the different correlations are compared and conclusions drawn.