INDUSTRY-BASED THERMODYNAMICS CASE STUDY ON REFRIGERATION CYCLE

ABSTRACT

The case study learning methodology has been used for more than 20 years in teaching science and engineering. This methodology is known to be highly effective in promoting students' understanding of the concepts and improving their ability to make connections between the concepts. In 2020 and 2021, the limited access to laboratory equipment and facilities due to the COVID-19 pandemic encouraged instructors to implement alternative methods. One of the alternatives considered in the current institution is the use of case studies to enhance students' understanding of thermodynamics and fluid mechanics topics during the online and hybrid implementations of those courses. In this study, an industry-based air-conditioning (AC) unit is facilitated to prepare a case study to teach refrigeration cycles in the laboratory part of thermodynamics. All four components of the AC unit, which include a compressor, a condenser, an expansion valve, and an evaporator, are assembled on a single platform. In an actual application, the compressor and condenser are part of the outside unit while an evaporator and expansion valve would be located indoors. In the first phase of the case study, students analyze temperature and pressure data for the normal operation of the unit to understand the function of each component in the cycle. In addition, by using thermodynamics property tables, they determine enthalpy and entropy values at different stages of the process, generate a temperature versus entropy (T-s) diagram, and calculate the efficiency of the AC unit. In the second phase of the study, they are provided with temperature and pressure data collected for the cases corresponding to when there is a problem with the AC unit. They perform analysis of those cases. The examples of issues introduced include part of the condenser or evaporator coils being disabled or using a partially blocked air filter. The equipment used in the case study is modified by the manufacturer to simulate those issues. During data analysis, student teams are tasked with identifying the issue introduced by looking at the changes in temperature, pressure, and T-s diagram. This paper provides detailed information about the case study, data collection, and analysis. Copyright © 2022 by ASME.