Heat pipes for dehumidification and Air Conditioning
The wrap around heat pipe is a heat pipe wrapped around a cooling coil. It consists of two sections, the pre-cool section placed before the cooling coil and the reheat section placed after the reheat coil. The wrap around heat pipe eliminates the need for reheat and increases the dehumidifying capacity of an air conditioner by as much as 91%. The technology uses about 50% less energy than electric reheat systems (hopefully you aren’t considering these) and about 25% less energy than other types of reheat.
5 Key Benefits of Using Wrap Around Heat Pipes
- Increase Moisture Removal of A/C Units. The first section of the heat pipe module precools the entering air. This causes the approach temperature of the air to the cooling coil to be lower. The result is, that as the air leaves the cooling coil, it is colder with a lower dew point and with less moisture in it. Depending on the design of the heat pipes, the cooling coil can be made to extract over 100% more moisture than one without heat pipes.
- Dryer Supply Ducts. After leaving the cooling coil, the air is reheated by the second heat pipe section. This lowers the relative humidity of the supply air. In a typical system, the relative humidity is lowered from nearly 100% leaving the cooling coil to approximately 70% leaving the second heat pipe section. This is in keeping with ASHRAE Standard 62-1989 which warns that if duct relative humidity exceeds 70%, fungal contamination can occur.
- Humidity Control. Buildings frequently encounter serious humidity problems that need to be addressed. Buildings used for specific purposes like hospitals, certain food processing plants, and some manufacturing plants require humidity to be kept at a low level. Wrap around heat pipes are usually the most efficient method of humidity control in these situations. By helping the A/C system remove more moisture from the air, the required humidity levels can be easily achieved.
- Energy Savings Through Passive Reheat. Since heat pipes provide reheat by utilizing the heat from the entering air, there is no requirement for active reheat and there is no net heat added to the space. Using heat pipes to replace active reheat results in substantial savings. A payback of one year may be achieved when electric reheat is replaced with dehumidifier heat pipes.
- Equipment Savings Through Downsizing. To cope with high humidity loads, the most frequently used technique is to oversize the A/C unit and then reheat the over-cooled air. This results in high operating cost as well as initial equipment cost. If dehumidifier heat pipes are used, over-sizing and active reheating can be avoided. With a chilled water system, wrap around heat pipes allow the designer not only to reduce the size of the cooling coil but also reduce the chilled water requirement, thus a smaller chiller unit can be used instead.
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