The majority of air-conditioning systems currently in operation is an all air system designed to control the indoor air temperature and humidity, and provide fresh, filtered air to building occupants.
The overall energy used to cool buildings with all-air systems includes the energy necessary to power the fans that transport cool air through ducts.
The capillary tubes system employs long-wave (infrared) radiation to the cooled surface to remove unwanted heat from the space. DOAS system supplies dehumidified air through its air distribution system. In its operation as an air-conditioning system. The capillary tubes system separates the task of sensible cooling from those of humidity controlled DOAS (Dedicated Outdoor Air System) with no recirculation of air.
Because cooling relies on radiation from a cooled surface to provide sensible cooling, the capillary tubes system can provide comfort at a higher indoor air temperature than an all air-system.
The capillary tubes system uses water as a cooling medium for radiant surface at a temperature of approximately 61° F (16° C). DOAS (Dedicated Outdoor Air System) supplied by ERV for ventilation air and humidity control.
Water is a better heating and cooling agent than air, because it would require a much larger volume (1000 times more) to transport the same heating and cooling capacity.
The smaller diameter of the tubes also provides a better homogeneity and higher thermal Efficiency (this efficiency is 98%). |
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| The thermal properties of water allow the capillary tubes system to: |
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| (1). Remove a given amount of heat from a building using 30% of the transport energy necessary for an all air-system to remove the same amount of heat |
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(2). Shift the peak cooling demand to later in the day.
(3). More easily interface with thermal energy storage systems.
Because the capillary tubes system can use large surfaces for heat exchange (usually the radiant surface occupies about 80% of the ceiling area or 50% of the vertical wall surface in a space), the temperature of the cooling water must be a few degrees lower (compared to air) than the room air temperature. This small temperature difference allows the use of either heat pumps with very high coefficient performance (COP) values, or of alternative cooling sources (for example, indirect evaporative cooling), to further reduce the electric power demand of the building. |
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By transporting only the air necessary for ventilation purposes, the capillary tubes system significantly reduces both the volume and the velocity of air-transported throughout buildings, thus practically eliminating noise and draft the same time, because the air does not play a major role for sensible cooling, it does not have to be cooled far below the room temperature. This reduces the problems caused by duct leakage and heat loss from ducts.
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Electrical Consumption:
Table 1 below summarizes the components of the electrical power demand of the all-air system and the capillary tube system. The values in the table show that the electrical power demand of the capillary tube system is only 71.5% of the electrical power demand of the all-air system. |
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Energy saving tips:
Three tips for the planning and mode operation of Capillary Systems can help keep energy costs low.
(1)The DOAS (Dedicated Outdoor Air System) and pumps should be adjustable to at least two speeds and should be switched to the lowest possible speed permitted by the time of day and temperature. Lowering the speed of the motor by half reduces energy consumption by 20%
(2) DOAS and ventilation devices should be generously proportioned to minimize the air velocity. If the air velocity is lowered by one-half, only one fourth of the energy is needed for the ventilators.
(3)The DOAS (Dedicated Outdoor Air System) should be regulated to prevent the air from being unnecessarily dehumidified and cooled..
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