Evaluation of thermal comfort in an office building served by a liquid desiccant-assisted evaporative cooling air conditioning system

Recent studies examined a liquid desiccant indirect and direct evaporative cooling assisted 100% outdoor air system (LD-IDECOAS) as an energy conserving alternative to conventional air conditioning systems. An IDECOAS was introduced as an environmental-friendly air conditioning system that uses latent heat of water evaporation to cool the process air. Recently, studies suggested the integration of a liquid desiccant(LD) system with an IDECOAS to overcome a cooling reduction in evaporative cooling performance in a hot and humid climate. The supply air (SA) temperature and humidity ratio of the proposed system depends on SA flow rate and removal moisture content. However, a supplying air flow method in a conventional variable air volume(VAV) system and a relatively unstable air conditioning performance of an indirect evaporative cooler (IEC) and direct evaporative cooler(DEC) in cooling seasons could cause SA temperature to fluctuate above and below the set point temperature, and this could result in occupants feeling uncomfortable in a conditioned zone. Therefore, the purpose of the present study involves estimating thermal comfort in an office building that is served by a liquid desiccant indirect and direct evaporative cooling assisted 100% outdoor air system (LD-IDECOAS). Predicted Mean Vote (PMV) method is selected to evaluate as to whether an indoor thermal environment complies with recommended comfort zone conditions as proposed by the ASHRAE Standard 55. The seasonal mode of operation of LD-IDECOAS is suggested and used to estimate thermal properties of supply air (SA) while serving the proposed system. Energy performance and thermal environment of a building model are predicted via a series of energy simulations by using a TRNSYS 17 program integrated with an engineering equation solver program. The simulation results indicate that LD-IDECOAS did not completely cool the conditioned zone occasionally in a cooling season. However, the results also suggested that the thermal environment in a conditioned zone is generally in compliance with the ASHRAE Standard 55. Accordingly, it is concluded that using the LD-IDECOAS in an office building can produce energy savings with an acceptable level of thermal comfort.