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Abstract
Cooling is very important for space conditioning of buildings in warm and humid regions. Along with the growth of cooling loads in modern buildings, the peak electricity demand increases during the day. This causes problems concerning the energy supply in some countries, such as Iran, as the demand for air conditioning occurs simultaneously with the maximum electricity demand of industries. The new solar cooling system presented in this article takes air from the outside by a wind tower, dehumidifies it with a desiccant wheel, cools it by an air-to-air heat exchanger (heat recovery system), and then cools it by a direct evaporative cooling system to the desired state of a maximum 100% relative humidity in the inlet air stream. The desiccant must be regenerated by heat. This can be achieved with solar energy from a solar air collector that is installed in the southern wall and roof of the building. In addition, the system is mathematically modeled. The model is used to simulate two hot and humid regions of Iran in the north (Babolsar) and south (Bushehr) over 1 year. The results show that this solar cooling system with a payback time of 5.5 years can provide 54% of the annual cooling load in the north and 48% in the south of Iran.
Nomenclature
| A | = | collector area (m2) |
| D | = | desiccant wheel diameter (m) |
| H | = | silica gel enthalpy (kJ/kg) |
| h | = | convective heat transfer coefficient (W/m2K) |
| I | = | solar radiation (W/m2) |
| k | = | convective heat transfer coefficient (W/mK) |
| L | = | convective heat transfer coefficient (W/mK) |
| M | = | air mass flow rate (kg/s) |
| Ra | = | Rayleigh number |
| Re | = | Reynolds number |
| Sc | = | Schmitt number |
| Sh | = | Sherwood number |
| T | = | temperature |
| V | = | velocity (m/s) |
| W | = | silica gel water content (kg water/kg air) |
Subscript
| a | = | air |
| b | = | beam radiation |
| c1 | = | collector inner cover |
| c2 | = | collector outer cover |
| d | = | diffuse radiation |
| f | = | fluid |
| m | = | desiccant matrix |
| p | = | absorber plate, process air |
| r | = | radiation heat transfer |
| r | = | regeneration air |
| α | = | absorption coefficient of plate |
| β | = | collector angle |
| τ | = | transmission coefficient of cover |