A non-intrusive method for evaluation ammonia mass flow rate in the condenser for diffusion-absorption refrigerators

Abstract

Studies of diffusion-absorption (DAR) refrigerators have intensified, as well as the market's interest in increasing energy efficiency through cogeneration systems. Several studies have been published with the objective of improving the coefficient of performance, through the most different procedures. This article evaluates a non-intrusive method for the calculation of the ammonia mass flow rate at the inlet of the expansion device. The required parameters are geometric data and condenser temperature. The air-side convection heat transfer coefficient was calculated considering six empirical correlations. Then, throughout an energy balance in the condenser, the mass flow rate was computed. Four correlations predicted similar heat transfer coefficient. Thus, it is possible to estimate the ammonia mass flow using only the geometric data and the condenser temperatures. The strategy adopted to achieve this goal it was to use only the geometric data and the temperatures of the condenser and to calculate the energy balance in the superheated and saturation phases, since the absence of the subcooling in the condenser is a characteristic of the DAR cycle.