Comparative analysis of the annual performance of a dedicated outdoor air system and a desiccant-enhanced evaporative air conditioner

Abstract

Dedicated outdoor air system (DOAS) and desiccant-enhanced evaporative air conditioner (DEVap) are two representative decoupled system that combines more than two air conditioning function. The former integrates the function of ventilation and latent cooling while the latter integrates the function of sensible cooling and latent cooling. Both the systems are well known for their energy saving potential; however, the performance of the systems should be analysed systematically to compare each system's energy performance. The aim of this research is to evaluate the energy performance of a DOAS and a DEVap in building applications comparatively. This paper compares the operating primary energy consumptions of both the DOAS and DEVap based on detailed annual energy simulation. For the simulation, the loads of the model building was simulated by using TRNSYS17 program and the operations of system components are simulated with the empirical models coded in commercial engineering equation solver (EES). Based on the simulations, the performance of DOAS and DEVap are evaluated in terms of cooling and dehumidification performance in addition to primary energy consumption. The study is composed of 6 chapters: 1) introduction; 2) literature review; 3) system description; 4) simulation overview; 5) simulation results; 6) conclusion. In chapter 1), research background, objectives and thesis outline are described. For the background, the concept of decoupled system and the basic information about DOAS and DEVap are presented Then, the process of the research is simply illustrated in the thesis outline. In chapter 2), the literature review of the systems are presented. In the literature review, the current research related to DOAS and DEVap conducted in open literature are described In chapter 3), the system components of DOAS and DEVap used in this study are described in detail with the system configurations. In chapter 4), the details of annual energy simulation is presented. First, the specific information related to the model building is presented. Then, the simulation model of each system component is described with the annual operation modes of DOAS and DEVap. In chapter 5), the results of the simulation are presented. First, for analyzing the cooling and dehumidification performance of DOAS and DEVap, the temperature and humidity ratio profile of the each process air that passed DOAS and DEVap are compared during the peak summer day. Then, the seasonal energy consumptions of DOAS and DEVap are compared based on the simulation results. In chapter 6), the conclusion drawn from the research is presented as follows: 1) During the annul energy simulation, DOAS and DEVap effectively controlled sensible and latent loads of the building by using energy recovery wheels and liquid desiccant and indirect evaporative cooling system respectively. 2) From the annual simulation result, DOAS that utilized ceiling radiant cooling panels for parallel cooling system consumed 22% less primary energy than DEVap. 3) The fuel energy was consumed in DEVap for regenerating the desiccant solution of the liquid desiccant system. The overall energy consumption of DEVap can be reduced to the great extent once it is applied with the renewable energy heating sources such as solar thermal system or fuel cells.