2016 ASHRAE Annual Conference

This seminar discusses the use of dry and liquid desiccant technologies and how to apply them creatively for the treatment outside air.  This includes a design that utilizes a combination of cooling tower water, chilled water and hot water that modulates with the outside air loads to either cool or heat the liquid desiccant to provide dehumidification or humidification of the outside air. Then, waste heat or onsite power generation to regenerate the liquid desiccant solution. A comparison of the two technologies will be presented and the opportunities for both to provide comfort and energy savings to meet ventilation codes.

The main purpose of this study is to propose a variable volume and temperature (VVT) control strategy for a liquid-desiccant and dew point evaporative cooling-assisted 100% outdoor air system (LDEOS) and evaluate its performance on a Building Controls Virtual Test Bed (BCVTB). For decades, various alternative air-conditioning technologies have been developed to reduce refrigerant use and energy consumption. Among them, many studies have been conducted on a liquid-desiccant (LD) and indirect evaporative cooling-assisted system because it independently controls the sensible and latent load and reduces cooling energy by using latent heat of water vaporization. In previous studies, the LDEOS, which conditions a space by using 100% outdoor air, is proposed by combining membrane enthalpy exchanger (MEE), LD, and dew point evaporative cooler (DP-IEC). Unlike the energy performance and the design process, few studies were conducted on the control strategies of the LDEOS. In the control strategy of a general variable-air-volume (VAV) system, the controller maintains a constant supply air temperature (SAT) for dehumidification control. However, the SAT control is hard to be implemented for an indirect evaporative cooler if VAV fan is applied. In this study, a variable-air-volume and temperature (VVT) control is presented for the LDEOS. In VVT, the cooling capacity is controlled by the fan airflow, but the SAT is not controlled. In the LDEOS, the dehumidification control is achieved by the LD, and thus, the SAT does not need to be modulated. The VVT control was realized on a BCVTB in a one-minute time step and evaluated its performance. The simulation result revealed that the proposed control strategy maintained a space comfortable while saving 35% of fan energy compared to the reheating-based constant SAT control strategy.

The main purpose of this research is to evaluate the energy performance of a liquid desiccant and indirect/direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) in a commercial passenger ship. The LD-IDECOAS consists of a liquid desiccant system, and indirect and direct evaporative cooler (IEC and DEC) for dehumidification, and sensible and adiabatic cooling of process air. This system was applied to cooling source from seawater and heating source was considered engine waste heat recovery system. The organic Rankine cycle (ORC) regression model from the existing literature was adapted as the waste heat recovery (WHR) system to evaluate waste heat thermal efficiency. For estimating the energy performance of the LD-IDECOAS, annual energy simulation is conducted for two cabins. The area of each cabin is 16.5m². The required thermal load of passenger cabins is estimated by according to ISO-7547 considering the typical operation condition. Consequent operating energy consumption of LD-IDECOAS is determined by using a commercial equation solver program.  The energy performance of the proposed system is compared with the conventional commercial passenger ship air conditioning system, which is using absorption chillers, for estimating the energy saving potential of the proposed system.