Entropy­based methods applied to the evaluation of a real refrigeration machine

Larisa Morozyuk,Sergey Gayduk,Andrii Moshkatiuk,Viktoriia Sokolovska-Yefymenko

doi:10.15587/1729-4061.2018.147710

Abstract

The aim of the research is the thermodynamic analysis of a real refrigerating machine with solid fouling on the heatexchange surface of an aircooled condenser with the help of entropy methods such as: the entropycycle method, the entropystatistical method and the entropy generation minimization method. The experimental data of the refrigerating machine with solid fouling in the form of dust on the external surface of the aircooled condenser was used for the thermodynamic analysis. The influence of irreversible losses in separate elements of the refrigerating machine caused by the presence of external solid fouling on the external heat exchange surface of the aircooled condenser was determined according to the entropycycle and entropystatistical methods. The entropycycle method has estimated the absolute value of energy losses in each element. The entropystatistical method was used to determine the excessive consumption of work in the real cycle in comparison with the theoretical compression process in the compressor. The irreversible losses associated with aerodynamics and heat transfer during air motion through a finned surface in an aircooled heat exchanger were estimated by using the entropy generation minimization theory. The influence of growing fouling on the thermal and mechanical components of the total entropy generation in the heat exchanger was determined. In addition, the fouling mass that determines the time of its cleaning was defined. Application of entropy methods for analyzing the real refrigerating machine at the design stage allows minimizing irreversible losses associated with operating conditions. Moreover, it allows predicting a maintenance schedule which contributes to energy saving

Highlights

Refrigerating machines and heat pumps with smallscale and medium-scale capacities are referred to the commercial refrigeration equipment
Встановлено вплив зростаючих вiдкладiв на термiчний i механiчний складовi загального виробництва ентропiї в теплообмiнному апаратi, а також визначено масу вiдкладiв, що зумовлює момент його очищення
Prediction of the rate of fouling deposition on the heat exchange surfaces of refrigerating machines is an unexplored problem. It consists in the presence of a large number of mutually influencing factors associated with the specific conditions of equipment operation

Summary

Introduction

Refrigerating machines and heat pumps with smallscale and medium-scale capacities are referred to the commercial refrigeration equipment. Analysis of the processes taking place in the elements of the refrigerating machine or the heat pump should be based on a clear understanding of the criteria of the design process. This will allow constructing an economic model of the machine and evaluating its operation in real conditions. Prediction of the rate of fouling deposition on the heat exchange surfaces of refrigerating machines is an unexplored problem. It consists in the presence of a large number of mutually influencing factors associated with the specific conditions of equipment operation

Objectives

Results

Conclusion