Build up of heating and cooling unit 27/7/2012

The heating/cooling unit (hcu) of the incubator is suppose to heat up the incubator chamber in a control way up to 50°C within 15-30 minutes and cool it down to 15°C within similar period of time. It was build up within a range of several days.

The computer power supply unit (PSU) producing 300 W ??? was used to power the hcu, fans etc. The central part of hcu consisted of aluminium based heat sink, dimensions 65 on ??? mm with five fins in parallel in the middle. This heat sink was insulated from outside by thin slice of insulation (what type???). Two peltier  modules were cleaned properly and thermal grease was applied on both sides of each of them. The 100 W peltier module was positioned on the left hand side of the heat sink, approximately in the middle with the heat generating side attached to the central heat sink. On the cold generating side of the peltier another aluminium heat sink with 21 fins and fan was attached. On the right side of the central heat sink 60 W peltier was attached again thermal grease applied on both sides. The cold generating side was attached to the central heat sink and heat generating side was attached to the aluminium based heat sink with fan, same dimensions as for the 100 w peltier. In both cases an insulation was cut out in the shape of peltier module so the module was directly attached to the heat sinks however around it, between the heat sings themsleves the insulation was places so the thermal exchange was minimised.
In order to keep whole hcu more stable, it was attached to the plywood desk (dimensions – 35 cm long; 13.5 cm broad and 3 mm thick). Everything was tight together with two plastic cable ties, making sure that all the heat sinks are in full contact with the peltier modules.

The hc unit was transferred on the top of the incubator. The PSU fan (dimensions 80x 80 mm) was used to move the air from the hcu to the incubator and back. It was placed directly in front of the hcu, blowing the air through the heat sink and secured to the plywood board by another cable tie. Cardboard and tape was used to create two enclosures to secure air tight circuit. One enclosure was placed before the fan and taped to the cardboard below and to the fan, it had approximately 10 cm long and 6.5 cm wide opening into the incubator chamber. Second enclosure was attached to the rear end of the central heat sink with approximately same size opening to the incubator chamber. Whole structure was taped by insulation tape and usual tape from both inside and outside to ensure that the circuit will be quite air tight and ready for testing.

Things to consider

The plywood used to secure the central heat sink should be removed so the heat sink is radiating heat directly in to the incubator chamber improving the heat transfer.


~ by algoldor on 07/08/2012.

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