An experimental investigation on the role of the operating time of the mist device on the thermal performances of a water-sprayed air-cooled condenser and on the energy consumption of the cooling system

• Water misting upstream of an air-cooled condenser allows to intensify heat transfers • The role of maintaining misting for a longer time on heat dissipation is investigated • An increase of 54.9% in the COP of the cooling system for two minutes of misting • 17.2% reduction in energy consumption of the cooling system • Heat transfer destruction and health risks associated to water misting can be avoided Water spraying upstream of an air-cooled condenser enables high heat dissipation. Meanwhile, a good control on the spray-heater parameters is crucial to avoid excesses of water and heat transfer destruction. This paper aims to experimentally illustrate the impact of the operating time of the mist device on the condenser thermal performances and the refrigerator energy consumption. To better visualize water stagnation phenomena, experiments are performed using a low pressure spraying device with 0.0065 L/min in water flow rate and 2-4 bar in pressure range. Several series of measurements have been performed on the refrigerant temperatures and pressures and on power consumption for different operating times of the mist device. Measured results showed that with 2 min of misting, the condenser inlet airflow and the refrigerant condensing pressure drop respectively from 32 to 27.4°C and 10 to 7.2 bar, while for 1 min of misting they decrease from 32 to 28°C and 10 to 7.6 bar, respectively. In this work, compared to the system without misting, maintaining the mist system in operation for 2 min allowed 54.9% enhancement in the Coefficient of Performance and 17.2% reduction in energy consumption. Consequently, the operating time of the mist device highly affects the condenser cooling performances and the refrigerator power consumption. Meanwhile, it is found that, above 2 min of misting, the condenser inlet airflow is saturated and the condensing pressure hardly changes while water stagnation is occurring. Hence, misting should be applied momentarily to avoid heat transfer destruction and water losses.