Application of radiant cooling as a passive cooling option in hot humid climate

In hot and humid region, air-conditioning is increasingly used to attain thermal comfort. Air-conditioning is highly energy intensive and it is desirable to develop alternative low-energy means to achieve comfort. In a previous experimental investigation using a room equipped with radiant cooling panel, it was found that cooling water kept to 25 °C could be used to attain thermal comfort under some situations, while water at such temperature would not cause condensation of moisture from air on the panel. This paper reports results of a series of whole-year simulations using TRNSYS computer code on applications of radiant cooling to a room model that represents the actual experimental room. Admitting the inability of radiant cooling to accept latent load, chilled water at 10 °C was supplied to cooling coil to precool ventilation air while water cooled by cooling tower was used for radiant cooling in daytime application. For night-time, cooling water from cooling tower supplied for radiant cooling was found to be sufficient to achieve thermal comfort. Such applications are considered to be more amenable to residential houses.     

Thermal comfort assessment and application of radiant cooling: A case study

A field assessment of thermal comfort was conducted at Mehran University of Engineering and Technology, situated in the subtropical region of Pakistan. The results show that people of the area were feeling thermally comfortable at effective temperature of 29.85 °C (operative temperature 29.3 °C). A comparison of this neutral effective temperature was made with the neutral effective temperature determined from adaptive models. It is found that the neutral effective temperature determined during this study closely match that of the adaptive model based on either indoor temperature or both indoor and outdoor temperatures. The results of thermal acceptability assessment show that more than 80% of occupants were satisfied at an effective temperature of 32.5 °C, which is 6.5 °C above the upper boundary of ASHRAE thermal comfort zone. Naturally ventilated classrooms and air-conditioned offices of the University were simulated using TRNSYS system simulation program for two cases, once when conventional air-conditioning is used for providing thermal comfort, and when comfort is achieved through radiant cooling. In the simulation, cooling tower was used to regenerate cooling water for the radiant cooling system. Energy consumption was estimated from simulation of both cases. The results show that it is possible to achieve thermal comfort for most of the time of the year through the use of radiant cooling without a risk of condensation of moisture from air on the radiant cooling surfaces. A comparison of the energy consumption estimates show that savings of 80% is possible in case thermal comfort is achieved through radiant cooling instead of conventional air-conditioning.