Heating and Cooling

Fluid Jackets

The pre-saturator, saturation and calibration chambers for the Mark 3 have been outfitted with fluid jackets which will have the ability to keep the temperature more uniform throughout the chambers. These fluid jackets will hold a 70/30 glycol-water mixture which will be used for heating and cooling. It was decided that fluid jackets were desirable for the heating and cooling, over a possible fluid bath for ease of accessibility within the system to make possible repairs, future changes and ease of manufacturing. If a fluid bath was implemented it would make for a lot of work to drain the fluid and ensure proper sealing throughout the entire system.

Condensing Unit

The condensing unit which will be used to provide cooling will also be designed in a way to provide additional heating by way of a hot-gas bypass loop. This hot-gas bypass is operated by a solenoid valve and routes the warm refrigerant exiting the compressor directly to the evaporator when cooling is not required.
A hot-gas bypass was selected based on the requirement of the condensing unit running constantly while the system is on. This is necessary to ensure that the large starting current of the compressor does not exceed the electrical load of the system while it is operating. Based on discussions with a local refrigeration company (Refrigeration Specialists), they recommended this hot-gas bypass and they also explained that by using the hot-gas bypass it will lower the heating requirements of the reservoir as this hot-gas will provide heating.

Cartridge Heaters

Heating in the system will be provided by two cartridge heaters. There is a 150W cartridge heater in the pre-saturator which will provide the heating needed for the distilled water to operate the system. A second cartridge heater will be located in the fluid jacket reservoir and will be used to warm the fluid for the jackets. This cartridge heater is 750W.