Predetermined overall thermal transfer value coefficients for Composite, Hot-Dry and Warm-Humid climates

This paper attempts to formulate Overall Thermal Transfer Value (OTTV) coefficients for Composite, Hot-Dry and Warm-Humid climates, the three main tropical climates in India. Four existing air-conditioned office buildings - two mid-rise and two high-rise were modeled as case studies using eQuest v.3.6, which is a DoE2.2, based building energy simulation tool. Based on the study of building envelope, loads, operation and HVAC system characteristics of these case study buildings, a hypothetical high-rise, 16 storey office building, octagonal in plan was created for parametric studies. 98 types of opaque exterior wall constructions and 93 types of glass constructions were varied sequentially in parametric runs to obtain results for hourly wall conduction, glass conduction and glass radiation heat flow in eight orientations for each of the climate type. These hourly results were processed to obtain annual heat gain intensities for each parametric case for all three modes of heat transfer. Regression analysis was used to obtain the OTTV coefficients - TD_eq, DT and SF for the three climates. A new OTTV equation is obtained and presented. The set of coefficients obtained were verified by calculating the OTTV for the four case study buildings, for various parametric runs. The computed OTTV for the four case study buildings exhibits good linear correlation with the annual space cooling plus heating energy use in three climates.     

An experimental investigation on passive cooling system comprising phase change material and two-phase closed thermosyphon for telecom shelters in tropical and desert regions

Advances in information technology have made the thermal management of telecommunication equipments more challenging over the past several years. As advances are being made the electrical energy consumption of telecommunication equipments is ever increasing and thereby increasing its dissipation rate. In addition such shelters are installed in remote areas, so cooling of telecom shelters becomes a great challenge for thermal engineers. A field study revealed conventional cooling systems are not so effective in terms of energy consumption and in the absence of power grid, shelters installed in such areas require additional capital cost to provide power for cooling system. A new passive cooling system incorporating phase change material (PCM) and two-phase closed thermosyphon (TPCT) heat exchangers has been developed and experimented to provide thermal management for telecommunication equipments housed in telecom shelters. The newly developed thermal system absorbs the equipment dissipated heat during the hottest part of the day, stores it as latent heat and releases it through thermosyphons during the night to the ambient.