T. O. Falade’s research while affiliated with The Federal Polytechnic Ado-Ekiti and other places

This paper presents the design, construction and performance testing of a refrigeration system for use as experimental apparatus for demonstrating vapour compression refrigeration cycle and basic concepts of thermodynamic principles. The apparatus shows the visual observation of all-important processes. The experimental data were analysed using the first and second laws of thermodynamics to determine the refrigerating effect, the net heat rejected from the system, the compressor work input and coefficient of performance (COP). During the test, the COPs of the system and Carnot cycle were found to be 3.87 and 6.96, respectively. Also, the steady state discharge pressure and the average refrigeration capacity obtained were 830 kPa and 915.8 W, respectively, while the relative and isentropic efficiencies obtained from the system were 55.6 and 86.7%, respectively.

In this paper, the performances of three ozone-friendly Hydrofluorocarbon (HFC) refrigerants (R32, R134a and R152a) in a vapour compression refrigeration system were investigated experimentally and compared. The results obtained showed that R32 yielded undesirable characteristics, such as high pressure and low Coefficient of Performance (COP). Comparison among the investigated refrigerants confirmed that R152a and R134a have approximately the same performance, but the best performance was obtained from the used of R152a in the system. As a result, R152a could be used as a drop-in replacement for R134a in vapour compression refrigeration system. The COP of R152a obtained was higher than those of R134a and R32 by 2.5 % and 14.7 % respectively. Also, R152a offers the best desirable environmental requirements; zero Ozone Depleting Potential (ODP) and very low Global Warming Potential (GWP).

This work is an attempt to utilise the benefits of using forced convection solar dryers through the use of a rotary wind ventilator in the remote areas where electricity and other power sources are non-existent. The solar windventilated cabinet dryer was designed, constructed and tested in Nigeria on latitude 7.5o N. The results obtained show that the temperatures inside the dryer and the air-heater were higher than the ambient temperature during most hours of the day-light. The drying of food items in the dryer was compared with open air-drying of similar items. Comparatively, drying with the solar cabinet dryer showed better results than open air-drying. The results also revealed the dependence of the dryer performance on the proper air circulation through the system. The system efficiency increased as the air velocity through the system increased. During the period of test, the average air velocity through the solar dryer was 1.62 m/s and the average daylight efficiency of the system was 46.7%.

As a result of global concerns over the depletion of the earth’s protective stratospheric ozone layer by the atmospheric release of chloroflurocarbons (CFCs) and hydrochlorofluoro-carbons (HCFCs) refrigerants, their production has been restricted and they are no longer choices for new equipment. This paper presents theoretical investigation of the performance of some environment-friendly refrigerants in a sub-cooling heat exchanger refrigeration system. Five promising environment-friendly refrigerants (R23, R32, R134a, R143a and R152a) were selected from methane and ethane derivatives and they were investigated theoretically. Sub-cooling heat exchanger was used to evaluate the impact of selected refrigerants on the exchanger effectiveness, system capacity and coefficient of performance (COP). The results obtained showed excellent performance of R152a and R134a, and fair performance of R143a when compared with R12 in vapour compression refrigeration system. The results also showed that using R23 and R32 in the refrigeration system will be detrimental to the system performance.