Hello I have calculated the capacity of the evaporator and the condenser of a refrigeration cycle but I need to determine the diameters of the coils. IS there any software used foe this?
Vielen Dank !
Refrigeration effect in Evaporator is rate of heat transfer. Use concepts of Heat exchangers with one cooling fluid at constant temperature and other at variable temperature. Use LMTD method and determine Surface if Heat transfer coefficients were known ( so that over all heat transfer coefficient is known).
use simple excel sheet calculations to do it. No need for software to get diameter.
For any help do not hesitate to post in this thread. i will help you.
Dear Ahmed S. Mansour
Currently, I'm working with vapor compression refrigeration cycle simulation. I am using VBA excel. Firstly, I am choosing the refrigerant, heat load. then I find the correlation heat transfer and pressure drop of evaporator and condenser based on other papers. Then, Selecting dimension (lengh or diameter, number of fins) based on trial error (the range each parameters are based on the paper) to find out which is compatible with my case.
Good luck
Thank you very much dear Srinvas Sharma Gangaraju and Teguh Hady Ariwibowo I am gonna try this and see :)
Viel Erfolg !
Hello everybody, here is an example from Yunus Cengel heat transfer reference. It shows how to carry out calculations on a radiator of a car. I need the same method to get the diameter but for the evaporator.
I guess we can use the same equations but with different boundary conditions and a slight modification in the temperature differences to get the logarithmic mean TD.
I have the refrigeration cycle properties (From the chart) How can we use it for the calculations? We have also the capacity of the evaporator + the inlet air temperature (35 C) outlet (23). Also I have the UA_total value. What should we do next? Thank you !
LMTD can be used only if the fluid properties is constant. in refrigeration cycle the refrigerant properti change drastically.
https://en.m.wikipedia.org/wiki/Logarithmic_mean_temperature_difference
However, in some paper they still use LMTD for Refrigeration cycle but they divide the length of Evaporator and condenser into small length so the properties difference is so small. hence, the LMTD still can be used
see the following example
https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1955&context=iracc
For UA, the most challenging is to define U because its calculated based on heat transfer coefficient from the refrigerant and air side. This could be obtained only by empirical correlation which is based on experimental result. because Nusselt number and friction factor depend on characteristics of each refrigerants.
It's better to see proper empirical correlation based on your refrigerant on some papers.
Hello, I have got the (UA)_total and LMTD values from coolpack software based on the evaporator capacity, temperature and other inputs at a specific refrigerant. Then we used these results and substituted in the equation sin the pdf equations at guessed Diameter and L values to see the result of the multiplication of U and A. We got the same value of U*A from the equations. So we can now change the value of the diameter and L and see the optimum values I guess. The factor was 1 at the current case.
Thank you
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