The application of heat pipe heat exchangers to improve the air quality and reduce the energy consumption of the air conditioning system in a hospital ward—A full year model simulation

Research was conducted to study the effect of heat pipe heat exchangers on the existing air conditioning system of a hospital ward located in Malaysia, a tropical region. The present research employs the transient system simulation software (TRNSYS) to study the hour-by-hour performance of the system in terms of supply duct air and indoor air conditions in the ward space. Fieldwork study showed that the existing air conditioning system operating in the Orthopaedic Ward, University of Malaya, Malaysia is not capable of providing the desired supply duct air and indoor air to the space. Therefore, the possibility of improving the air conditioning system by adding heat pipe heat exchangers was investigated. The impact on energy consumption, power savings, supply duct air and indoor air with heat pipe heat exchangers incorporated in the air conditioning system were simulated and the results were compared with the existing system.Based on the present research, the system with the added eight-row heat pipe heat exchangers is recommended to provide convenient and healthy air into the ward space according to the ASHRAE recommendations. Moreover, it was found that by applying the new design, a considerable amount of energy and power could be saved.     

New counter flow heat exchanger designed for ventilation systems in cold climates

In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure drop.     

空气源热泵风侧换热器上湿空气状态的计算机模拟

用计算机模拟空气源热泵风侧换热器在不同环境温度和相对湿度条件下运行的热力特性。计算出换热器肋片管表面温度后，根据水的相图判别肋片管上湿空气的干工况、凝露和结霜三种状态。模拟结果表明，环境温度5℃左右，相对湿度高于67％，风侧换热器肋片管易结霜；环境温度越低，则越不容易结霜。     

Performance testing of a counter-cross-flow run-around membrane energy exchanger (RAMEE) system for HVAC applications

A novel run-around membrane energy exchanger (RAMEE) system is designed, built, and tested for heating, ventilating, and air-conditioning applications. The RAMEE system consists of two counter-cross-flow liquid-to-air membrane energy exchangers, one located in the supply and the other in the exhaust air streams of a building. Inside each exchanger, a micro-porous membrane separates the air and desiccant solution streams. This membrane allows heat and water vapor exchange between the two streams. The RAMEE system thus exchanges sensible and latent energy between the supply and exhaust air streams by using a desiccant solution as the energy carrier that is pumped in a loop between the two exchangers. The RAMEE performance is evaluated by testing the system with various air and desiccant solution flow rates during standard summer and winter operating conditions. During summer test conditions, the total system effectiveness increases with increasing desiccant flow rate, but decreases as the air flow rate increases. Under winter test conditions, the total effectiveness changes little with changes in the air and desiccant flow rates. For some test conditions, the maximum total effectiveness of the system is between 50 and 55%. The effectiveness data are compared to available correlations and reasons for discrepancies are discussed.     

Condenser heat recovery with a PV/T air heating collector to regenerate desiccant for reducing energy use of an air conditioning room

This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%.     

A study on modeling and performance assessment of a heat pump system for utilizing low temperature geothermal resources in buildings

Low and moderate geothermal resources are found in most areas of the world. A very efficient way to heat and air-condition homes and buildings is the utilization of ground source heat pumps (GSHPs), also known as geothermal heat pump (GHPs), to obtain heat energy from low temperature geothermal resources.