Abstract
Opened air cycle is a promising sewage concentration technology using heated air as the medium to absorb water from the sewage. Unlike closed cycles, the air flow is directly ejected out of the system after humidification in opened cycles. Operating conditions and the circle’s efficiency are highly affected by the weather, such as the time-varying ambient temperature and relative humidity. Since the evaporating temperature relies on the ambient temperature, to restrain its dependence, the evaporator was proposed combined with the ejected air flow in this paper. Such a design could improve the efficiency of the heat pump by increasing its evaporating temperature. Simulation of the newly proposed open sewage concentration cycle was performed to investigate its thermal process and economic efficiency under actual weather conditions. Thermodynamic models of the compressor, heat exchangers and the sewage concentration chamber were established. Climatic conditions at Xi’an, China were referenced as actual weather conditions. Optimisation of the working parameters was performed to achieve higher economic index. The results demonstrated that the average monthly power consumption of the optimized cycle was 0.3508 kWh/kg. Compared with the published data of the closed cycle, the total cost of new opened cycle was nearly one-third lower.
Highlights
With the development of industry, sewage treatment demands are increasing year by year
Influencing factors of system performance By calculation, the change of air relative humidity has small influence on the system performance compared with other variables, so this paper mainly studies on the influence of other three variables: inlet air temperature, evaporating temperature and condensing temperature
The chamber temperature rises with the air temperature, and inlet air flow rate decreases due to constant refrigerating capacity, which leads to reduced evaporation mass flow, causing emoney increasing
Summary
With the development of industry, sewage treatment demands are increasing year by year. As a kind of efficient and energy-saving wastewater concentration technology, heat pump drying technology solves the problem of difficult structural design and fouling[3] in MVR[4,5] and membrane process[6]. It can be applied in atmospheric pressure and low ambient temperature, which has obvious advantages for heat sensitive sewage[7,8]. Such technology has broad prospects for application in actual industry
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More From: IOP Conference Series: Materials Science and Engineering
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