Reference no: EM132163901

Assignment -

Assume that you are a refrigeration engineer and you are required to produce a written report on the energy performance of the refrigeration system you have tested in the laboratory. You have carried out steady state tests for three condenser water leaving temperatures (approximately constant refrigerant condensing temperatures (saturated vapour)) and a range of evaporator water leaving temperatures (constant refrigerant evaporating temperatures (saturated vapour)). You are expected to:

Task 1 - Plot the performance characteristics (performance maps) of the refrigeration system as functions of the condenser water leaving and evaporator water leaving temperatures. These characteristics should include power consumption, cooling capacity and COP.

Task 2 - Calculate and plot other characteristics (efficiencies) that you may feel are relevant to your discussion and the performance evaluation of the system.

Task 3 - Calculate and Plot the Carnot COP and compare it with the actual COP of the system discussing the main reasons for the difference in the two values.

Task 4 - Discuss the performance characteristics of the system and their implications with respect to system design and optimal operation.

Advice -

Try to address all the above points in your report. Your main report should not be more than 10 pages A4 size (including graphs) and should be typed or produced on a word processor; sample calculations which should be included in an Appendix may be hand written.

You may use a spreadsheet package to facilitate your calculations. All the experimental results are written in Excel format on the disk provided. For your calculations you will need the properties of R404A. You can read these properties from the property tables given in the attached file (R404A_Properties.pdf) or the P-h Chart shown in Appendix C. Please note that the pressures in the tables and chart are in absolute values. The pressure readings in the Excel file on your disk have already been converted to absolute values. In addition, R404A is a near-azeotropic mixture of HFC- 125/143a/134a, 44/52/4% by weight. It is a non-ozone depleting compound, designed to serve as a long-term alternative to R502 and R22 in commercial refrigeration applications. Compared to pure refrigerant, at constant temperature in saturation region, the R404A pressures of saturated vapour and liquid are slightly different, as shown in the provided property table and p-h Chart in Appendix C. On the other hand, at constant pressure in saturation region, the R404A temperatures of saturated vapour and liquid are also a little varied.

Please also note that enthalpy and entropy properties taken from the tables and the Chart for a given refrigerant state may be different. This is because different refrigerant manufacturers use different origins to calculate enthalpies and entropies. Irrespective of whether you use the chart or tables you should arrive at the same answer because although the absolute values of the properties may be different the difference between the absolute values at the beginning and end of a process will be the same. What is of the interest is the change in enthalpy or entropy during a process and not the absolute values at the beginning and end of the process. It is important therefore not to mix enthalpy and entropy properties taken from the charts or tables if these have been produced by different chemical companies.

The experimental test facility and experimental method are described in Appendices A and B respectively.

You can make your own assumptions where necessary but make sure to specify these assumptions and clearly justify them in your report.

Attachment:- Assignment Files.rar