Here is my latest undertaking in refrigeration. I always wanted a portable means to cool a container of food or air condition a small space. Using spare parts lying around I decided to create a tiny packaged air conditioning unit.
I have the compressor from a small ice maker. It works great and I did use it to chill a battery box. I have since decommissioned it and left it parked up for the past 2 years. Now I decided to make an air conditioner for future uses.
Peltier coolers have extremely low EER versus refrigerant based systems. I wanted maximum cooling via this 100watt, 15lb, R143a based compressor. This project is powered via household 120Volt, 60Hz AC.
This project requires patience and skills. It is not hard but takes some time.
Step 1: Fabrication of an Air Exchanger.
Using a 2 inch pvc pipe, I secured a 12 volt blower fan to one end using a long cable tie. I had to drill through the pipe to do this. I put evostik followed by silicone adhesive (the 2 unsung heroes) to seal around the fan and pipe.
Step 2: Slotting the Air Exchanger Onto the Compressor.
The 2 inch pipe slides perfectly onto the cold part of the ice maker. I had to do some careful bending of the refrigerant lines to make everything into a compact form.
The diy cold air exchanger will be right on top the radiator fins. I put some thermal insulation wrap to minimize heat ingress into the cold air exchanger.
I sloped the air exchanger so the blower fan is higher. I don't want water pooling at the motor. The lower end I will put a drain tube to let the condensed water out.
Step 3: Making a Housing for Everything.
I had a document storage box that I stored some electronic items. Emptying it I cut out 2 square areas for the radiator and cooling air intake. I also cut holes for the air suction and discharge ports.
Due to the low weight of the compressor, the cover and handle for this box will make it easy to carry it around.
Step 4: Mounting the Compressor Into the Box.
The base of the compressor has 4 mounting bushings. I secured 2 diagonal bushings with nuts, bolts and washers to the base of the box.
For the suction and discharge air, I used 3/4inch pvc male threaded fittings to allow standard garden hose connections to the outside of the box.
I put a removable sponge air filter for the cooling air intake.
Step 5: Wiring the Controls.
I had previously wired a 120volt digital temperature controller (STC 1000) with two 12volt power supplies into a pvc box. One 12volt supply stays on once the 120volt AC power is applied. The other 12volt supply, on the right, is switched on with the compressor. I attached the pdf manual for the STC 1000 controller for your convenience.
The radiator and air exchanger blower fans I have running all the time to keep the compressor cooler. Both are powered by 12VDC.
I bolted the controller box onto the outside of the chiller housing and routed the wiring through a hole in the pvc and chiller boxes.
The thermal sensor I placed on the pvc elbow of the discharge air. This way I have a reasonable representation of the chilled air temperature. The actual air temperature is about 6C lower but I prefer a less optimistic reading.
Step 6: Adding Heat Shielding.
Using an old windscreen sun shield, I cut lengths and fit them to partition the compressor from the air exchanger. Basically I made a lower "hot section" in the enclosure box and an upper "cold section". The windscreen shield material is exceptionally well designed for this purpose and it is extremely low cost.
Doing this task alone allowed greater than 14C temperature difference between ambient and the discharge air in recirculation mode.
Step 7: Adding a Condensate Drain Line.
Everytime the compressor cycles, accumulated frost will melt and trickle out of the cold air exchanger. Normally it would collect in the enclosure box but I wanted it to come out of there. I used a 3 inch length if 1/4inch copper tubing and a length of pvc tubing to drain this condensate out.
I used silicone adhesive to make the air exchanger air tight to allow greater efficiency of entire unit.
Step 8: Testing!
Allowing the unit to run in non recirculation mode, that is just blowing out cold air, I took thermal measurements of the suction and discharge.
With an ambient temperature of approximately 29C, the discharge can chill air down to 16C which is amazing. In recirculation mode the chiller will be even more efficient and will achieve a greater temperature difference.
I noticed that the discharge air gets coldest when the suction flow is reduced by partially blocking the port or reducing the blower fan speed in the cold air exchanger. Apparently slow flow across the cold fins allows for greater heat extraction.
Step 9: Making It Truly Portable
In order to safely take the weight of the small compressor, I inserted 2 bolts at each corner of the lid. These ensure the plastic clip to snap the lid closed does not fracture when I'm lifting the chiller.
Step 10: Real World Applications.
This air chiller I made for future uses. I want it as a chill unit for an air line respirator. This will allow me to work comfortably in enclosed ceiling areas or anywhere that is too damn hot.
The next application is to chill food in an insulated box. I will simply cut two 1inch holes to allow suction and discharge air to flow and food inside will be cooled until a proper refrigerator is found.
The possibilities are exciting. Stay tuned for future updates!