Heat Exchanger Design of Direct Evaporative Cooler Based on Outdoor and Indoor Environmental Conditions

Abstract

Performance of a direct evaporative cooler (DEC) was numerically studied at various outdoor and indoor air conditions, with geometric and physical characteristics of it being extracted based on thermal comfort criteria. For this purpose, a mathematical model was utilized based on the equations of mass, momentum, and energy conservation to determine heat and mass transfer characteristics of the system. It is found that the DEC can provide thermal comfort conditions when the outdoor air temperature and relative humidity (RH) are in the range of 27–41 °C and 10–60%, respectively. The findings also revealed that by raising the RH of ambient air, the system will reach the maximum allowed RH faster and hence a smaller heat exchanger can be used when the ambient air has higher RH. Finally, performance of the DEC in a central province of Iran was investigated, and a design guideline was proposed to determine size of the required plate heat exchangers at various operating conditions.

Optimal operation of evaporative cooling pads: A review

“…Larger humidity increase is at the same time evidence of larger temperature drops; in this sense, Sellami et al [99] found that the outlet temperature was lower as the inlet relative humidity increased. Gilani and Poshtiri [100] indicate that smaller spacing among plates is needed as the air relative humidity increases, then provide a guide for the design of this plate spacing depending on the air conditions. However, despite the effect of the inlet air psychrometric conditions on the temperature and humidity variation, simulation results show a negligible effect on the saturation effectiveness [69,99].…”

Effectiveness enhancement and performance evaluation of indirect‐direct evaporative cooling system for a wide variety of climates

“…The equations of conservation for air flow and water stream for DEC are expressed as follows [5]: For mathematical modeling of IDEC, co-current DEC and f-type IEC have been selected.…”

“…A DEC was modeled mathematically based on the equations of mass, momentum, and energy conservation to obtain heat and mass transfer characteristics of the system. It was concluded that the modeled system was able to provide thermal comfort conditions when relative humidity and the outdoor air temperature are in the range of 10–60% and 27–41°C, respectively . Two‐stage indirect/direct cooler was modeled mathematically.…”

Thermal performance analysis of a naturally ventilated system using PMV models for different roof inclinations in composite climatic conditions

“…A study done by Orme has suggested that the energy consumption by HVAC systems in the residential building is nearly about 68% of the total consumption [20], which can be reduced significantly. Researches have been done to maintain [21,22] and improve [23][24][25] the thermal environment of buildings along with increasing its energy saving potential. However, one of the best passive approaches for reaching these target reductions in energy consumption in HVAC systems is to utilize increased natural ventilation, which would lead to an exchange of air with the outside surroundings and would also lead to the circulation of air within the building, without the help of any mechanical systems.…”