Searching for the energy efficient operation modes of absorption refrigeration devices

Abstract

The work demonstrates advantages of absorption refrigeration devices (ARD), as well as their essential shortcoming - a larger, in comparison to the compression analogs, energy consumption. In this connection, the main directions are examined of increasing energy efficiency of absorption refrigeration devices and the prospect of direction of improving the systems of automatic control is substantiated. It is shown that the only controlling influence on the efficiency of the ARD performance is achieved by the thermal power supplied in the generator-thermosyphon. Based on the analysis of the processes of heat mass exchange and the modes of flow of vapor-liquid water-ammonium mixture in the ARU generator-thermosyphon, the ambiguous influence of numerical values of the height of the lift part of the generator on energy characteristics of a standard ARU is shown. On one hand, this increase in height leads to the increase in hydraulic resistances at the motion of the VLM flow and heat losses, on the other hand, there appears a possibility of increasing the surface of heat mass exchange in the absorber. We run analysis of the effect of ambient temperatures on the ARD and ARU energy efficiency and the conditions of optimal operation. To examine the working modes of real objects, we carried out experimental studies of the modernized one-chamber ARD "Kiev-410" with a low-temperature compartment (LTC) of the Ash-160 type (manufactured by Vasilkovskiy Plant of Refrigerators, Ukraine) We obtained a set of quasi-static performance characteristics of the modernized one-chamber ARD "Kiev-410" with LTC of the Ash-160 type along the channels "thermal power supplied to the ARU generator - temperatures of the surface of the ARU elements in control points" at different conditions of heat removal from the external surface of dephlegmator (nominal, intensive heat removal, thermal insulation along the entire length of dephlegmator). As a result of conducted studies of the real object, we selected 5 types of the working modes of generator: optimal by energy efficiency (III), "waiting" (II), "accelerating" (IV) and two non-working modes (I and V). It was shown that at modes I and V the refrigeration cycle of ARU is not realized. Mode II may be used by designers when working with positional algorithms of control as the "waiting" mode, which ensures the state of "readiness" for the rapid start; mode IV - as the "accelerating" at the start of ARU from non-operating state to the rapid attaining of the working load.