Testing Refrigerants and Capillary Tubes to Find Peak Performance

Click this link https://boot.dev/?promo=HYPERSPACEPIRATE and use my code HYPERSPACEPIRATE to get 25% off your first payment for boot.dev. In this video I'll show how I built a test fixture to measure the Heat Lift and Coefficient of Performance (COP) versus. Temperature for three different refrigerants using different capillary tube diameters or an electronic expansion valve (EEV). The refrigerants used are R600 (N-butane, not R600A which is Isobutane), R134a, and R290 (Propane). The reason I chose to use N-butane instead of Isobutane was to evaluate its performance as a very low pressure refrigerant, which I have a use for in some future projects. These three refrigerants were chosen for the tests because they're easy for individuals to access through retail suppliers (at least in the United States), as opposed to higher pressure synthetics like R410, R454, R32, and so forth. They're also more suited to a lower pressure system based off an R600A or R134a reciprocating compressor. The capillary tube diameters that were tested were 0.6, 0.8, and 1.0mm inner diameters, all with a length of 400mm. Note that length of the capillary tube is far less important than its inner diameter, since most of the pressure drop happens in the first 10-20 percent of the length. These tubes were tested individually and in parallel using a selector valve manifold. I also intended to test with an Electronic Expansion Valve (EEV), but accidently destroyed part of the system before I was able to. However, I was able to create a comparison table running both the EEV and the capillary tubes on compressed air to show that the tubes tested in this video fell within about the first 20 steps of the expansion valve (with 200 steps being fully open). Heat lift is measured with a large evaporator wrapped with heater pads that are controlled by a bench power supply, and temperature is measured at the outlet of the evaporator. Coefficient of performance can then be determined by dividing the heat lift by the power input. Initially my COP numbers were somewhat weak until I realized I was running an average power factor of about 0.62, meaning they were higher than I originally believed. With R134a and Butane, a COP of 2.0 was reached at about 6C, and 2.5 was reached at 12C, putting the energy efficiency on par with a residential air conditioner unit. At -21C with R134a, a COP of 1.0 was measured, which is reasonable performance for a real world application. Propane and Butane both underperformed R134a somewhat, but this was to be expected since they were too high or too low pressure (respectively) for the compressor, which was made for R134a (part number B38H5). Anyway, I hope this test data is helpful for anyone trying to build their own DIY refrigeration systems, since I constantly get questions asking about whats compressors, refrigerants, capillary tubes or expansion valves to use, and so forth. Check out the link below for the raw test data. Raw Test Data: https://docs.google.com/spreadsheets/...