Jinzhe Nie

Experimental Study of a Low-Temperature Power Generation System in an Organic Rankine Cycle

AbstractThis paper presents a new power generation system under the principle of organic Rankine cycle which can generate power with a low-temperature heat source. A prototype was built to investigate the proposed system. In the prototype, an air screw compressor was converted into an expander and used as the engine of the power generator. The style of the preheater was a shell and tube heat exchanger, which could provide a long path for the working fluid. A flooded heat exchanger with a high heat transfer coefficient was taken as the evaporator. R134a was used as working fluid for the Rankine cycle in the system. This study compared and analyzed the experimental performance of the prototype at different heat source temperatures. The results show that the preheater and flooded evaporator was used for sensible heating and latent heating of the working fluid, respectively, as expected. When the temperature of the heat source increased, the pressure at the inlet of the screw expander increased, and the mass ...

Experimental evaluation of enthalpy efficiency and gas-phase contaminant transfer in an enthalpy recovery unit with polymer membrane foils

Experimental studies were conducted in a laboratory setting to investigate the enthalpy efficiency and gas-phase contaminant transfer in a polymer membrane enthalpy recovery unit. One commercially available polymer membrane enthalpy recovery unit was used as a reference unit. Simulated indoor air and outdoor air by twin chambers was connected to the unit. Three chemical gases were dosed to the indoor exhaust air to mimic indoor air contaminants. Based on the measurements of temperature, humidity ratio, and contaminant concentrations of the indoor exhaust air and outdoor air supply upstream and downstream of the unit, the temperature efficiencies, humidity efficiencies, enthalpy efficiencies, and contaminant transfer ratios were calculated. The results showed that over 60% of enthalpy recovery efficiency could be achieved and that the contaminant transfer ratios were in the range of 5.4% to 9.0%. The enthalpy efficiency in cold–dry climate conditions was slightly higher than in hot–humid climate conditions.The contaminant transfer ratio were independent of any hygrothermal difference between indoor and outdoor air and was unrelated to its molecule size or water solubility. The conclusion indicated that the polymer membrane enthalpy recovery unit may be a viable choice for energy recovery in ventilation systems.

Experimental Evaluation of a Total Heat Recovery Unit with Polymer Membrane Foils

A laboratory experimental study was conducted to investigate the energy performance of a total heat recovery unit using a polymer membranes heat exchanger. The study was conducted in twin climate chambers. One of the chambers simulated outdoor climate conditions and the other simulated the climate condition indoors. The airflows taken from the two chambers were connected into the total heat recovery unit and exchange heat in a polymer membrane foil heat exchanger installed inside the unit. The temperature and humidity of the air upstream and downstream of the heat exchanger were measured. Based on the measured temperature and humidity values, the temperature, humidity, and enthalpy efficiencies of the total heat recovery unit were calculated. The experiment was conducted in different combinations of outdoor climate conditions simulating warm and humid outdoor climates and air-conditioned indoor climate. The test was also conducted in isothermal conditions to observe the moisture transfer performance of the polymer membrane heat exchanger. The results of the experiment shows that total heat recovery equipment tested can recover up to 60 % of the total heat from the ventilation air. Around 87 % of the recovered total heat is latent heat that comes from the moisture transfer.