Expansion Devices

Page 1 of 4 Expansion Devices I. intro Expansion devices are basic components of a refrigeration system which cover out two major calculates (1) the insisting reduction from the condenser to evaporator pressure sensation and (2) the regulation of refrigerant flow into the evaporator. These elaboration devices can be mainly classified into two symbols which are namely the fixed fount type (flow area is fixed) and the variable opening type (flow area changes correspondingly with a change in mass flow rates).There are about septenary basic types of refinement devices for a refrigerant in a refrigeration system. These include capillary tubing subways and orifice which are under the fixed opening type and the manual expansion valves, automatic expansion valve (AEV), thermostatic expansion valve (TEV), electronic expansion valve and waste type expansion valve which are tout ensemble under the variable opening type. The float type expansion valve is upgrade classified into h igh side float valve and low side float valve (Arora, 2006).One of the most commonly used expansion device is the capillary tube. For the purpose of this exercise, a computation related to it will be performed. In a lesson guide on expansion devices prepared by Prof. R. C. Arora in 2006, he/she defined a capillary tube as a long, qualify tube of constant diameter. The word capillary? is a misnomer since surface stress is not important in refrigeration application of capillary tubes. representative tube diameters of refrigerant capillary tubes range from 0. 5 mm to 3 mm and the lengths range from 1. 0 m to 6 m. II. Objectives The exercise was conducted to inform the students with expansion devices, its functions and its importance. Specifically, the objectives were 1. ) to examine the construction of some commonly-used expansion devices and 2. ) to assess the operation of some commonly-used expansion devices. III. Methodology A. Lab-Scale Refrigeration System A lab-scale set-up for a refrigeration system in the refrigeration laboratory was observed for the set up of expansion devices on the pressures at various points within the system.Three different types of expansion devices which are namely the capillary, constant-pressure and thermostatic expansion devices are activated by opening their corresponding valves. The reading at each of the five pressure reading points was recorded for every 2 to 3 minutes until they begin stable. An image of the observed set- Page 2 of 4 up was taken and the locations of the pressure-reading points were labelled. See Appendix A for the image. B. Computation Capillary Tube For the stabilised care fors of the condenser and evaporator pressures measured, the required theoretical length of the capillary tube was computed.The results were then compared with the actual length of the capillary tube observed in the laboratory. See Appendix B for the value of the computed and measured length of capillary tube. IV. Answers to Qu estions 1. In the computation part above, is there a discrepancy amid the actual and the calculated length of capillary tube? Explain. Based on Table 1, there is a discrepancy between the computed and measured value of the capillary tube. First, it must be noted that throughout the computation, assumptions were made.Upon realizing the difficulty of obtaining a value for the mass flow rate, a reasonable value of it was assumed. This could demand the obtained theoretical length of capillary tube since some of the parameters involved in the computation require its use. Simply said, the theoretical length would either summation or decrease depending on the assumed value but neer equal to the actual length, unless the like mass flow rate solely applies to the actual system (which might not really be the case).This is the same explanation behind the other assumed parameters. Additionally, the measurement of quantities necessary for computing the length of capillary tube is also sub ject to many accomplishable errors. This may include errors collect to the limitation of the instruments or devices or due to some human inflicted errors. From the computed percent error, it can be inferred that the two value for capillary tube length deviate from each other at the specified percentage. V. References Arora, 2006. Expansion Devices. pdf file Available at . VI.Appendix A. Figure with labels Page 3 of 4 PRESSUREREADING POINT 5 PRESSUREREADING POINT 1 PRESSUREREADING POINT 2 PRESSURE READING POINT 3 PRESSUREREADING POINT4 Fig 1. An image masking the pressure reading points in a lab-scale set-up for a refrigeration system B. Tabulated data Table 1. Measured and computed length of capillary tube Quantities veritable length (m) Theoretical length (m) Percent error (%) Values 4. 1 7. 17 42. 82 Note Computations on how I arrived with these values are in the spreadsheet submitted with this report. Page 4 of 4