In an open car park, the car cabin can accumulate huge amount of energy from the sun through direct and indirect solar radiation which raises the cabin temperature rapidly. It can cause hazard to car occupant, both human and pressurized goods. Sudden exposure to high temperatures may cause heat stroke which affects the brain’s temperature control and results to dizziness, confusion, loss of consciousness, and death. One of the problems that car users experience today is having a hot cabin that is exposed to direct sunlight for a long time. Hence, staying inside the car immediately would mean not only discomfort but also unsafe driving conditions to occupant and driver.
There are many ways to dissipate the heat inside a car. One way for this is through spray-cooling, fogging or misting. Spray cooling systems aim to control the climate inside a medium (i.e, greenhouse) to prevent thermal stress. It is based on a very fine droplets sprayed in the area which then evaporates during their fall resulting to a cool temperature. Based on ASHRAE, air conditioning systems can achieve this temperature by fanning the absorbed warm air over cold refrigerant-filled coils to cool an area. This process needs to remove a huge amount of heat load before human satisfaction is achieved. It also leads to wear and tear of the unit. Using the concept of fogging/spray cooling, rapid reduction of the temperature can be achieved. Since spray cooling is made up of tiny water droplets, it can cool an area faster because water’s specific heat capacity [4.18kJ/(°C x kg)] which is 4x that of air [1.01kJ/(°C xkg)]. It also has larger surface area which allows a large amount of heat convection. Thus, A.3. Properties of Saturated Water can be used as a pre-cooler for the air conditioning unit, reducing the heat load needed to cool an area. The use of a liquid as a medium to dissipate waste heat offers significant potential for high-heat-flux thermal management owing to the superior thermal properties of liquids relative to air.
An effective and economical solution to alleviate heat stress is through evaporative cooling system such that the indoor temperature is reduced. Evaporation can still take place even if the indoor air humidity is relatively high, which is an advantage of spray cooling/fogging systems. During evaporation, the respiration tract or the wetted body surface temperature drops relatively at high ambient air humidity. Preserving comfort while inside the cabin though the humidity is relatively high.
The Spray Cooling System was designed, fabricated and installed to a car which is totally exposed to direct and indirect solar radiation while parking. The relative cabin temperature drops were determined while the coefficient of performance of the air conditioning unit was calculated to further assess the pre-cooler’s capacity to minimize the wear and tear.The applicability of a spray-cooling device was tested as it was being used to pre-cool the cabin before cooling it further using the built-in air conditioning unit of the car.