Temperature–heat diagram analysis method for heat recovery physical adsorption refrigeration cycle – Taking multi-stage cycle as an example

et al. 2019

Energy

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The composite sorbents of MgSO4-impregnated zeolite 13X and activated alumina are developed for thermal energy storage (TES) with different temperature ranges. The sorption and desorption characteristics of raw and MgSO4-impregnated activated alumina are studied, and the performances of the selected sorbents are tested in a closed-system TES device. The results are compared with those of raw and MgSO4-impregnated zeolite 13X. It is shown that the impregnated MgSO4 improves the overall TES performances of zeolite 13X and activated alumina. Compared to the raw host matrices, the impregnated MgSO4 remarkably accelerates the temperature-rising rate of zeolite 13X to about three times and improves the temperature lift of activated alumina by 32.5%. The experimental energy storage densities of MgSO4-impregnated zeolite 13X and activated alumina are 123.4 kWh m −3 and 82.6 kWh m −3 , respectively. The sorption temperature region of activated alumina is more aligned with the preferred hydration temperature of MgSO4 in comparison with zeolite 13X. The hydration characteristics of MgSO4 can resolve the solution leakage issue of open systems.Thermodynamic analysis is conducted to evaluate the performances of the TES device with different sorbents.It is found that entransy can be used to assess thermally and electrically driven TES systems reasonably.

Section: Thermodynamic Analysismentioning

confidence: 99%

Performance characterizations and thermodynamic analysis of magnesium sulfate-impregnated zeolite 13X and activated alumina composite sorbents for thermal energy storage

et al. 2019

Energy

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“…In Figure , the shadow area enclosed by the hot and cold composite curves represents the irreversible loss in the heat transfer process, ,, which is also equal to the entransy dissipation rate . Therefore, the calculation of the irreversible loss in the HEN–ORC integration can be expressed as where T h and T c are the temperatures of hot and cold streams, respectively.…”

Section: Thermodynamic Analysismentioning

confidence: 99%

“…19 To simplify the problem, we focus on the heat recovery quantity and quality of the HEN−ORC integration with the isentropic efficiencies of the turbine and the pump assumed to be the fixed values in this study. The temperature−heat flow diagram (T−Q diagram) 20,21 is used to graphically analyze the influence of the working fluid and operating conditions. In this case, optimizing the heat recovery quantity and quality is the same evaluation criterion as maximizing the net power output.…”

Section: Introductionmentioning

confidence: 99%

Multiobjective Optimization Method for an Organic Rankine Cycle Integrated with the Heat Exchanger Network

Chen

et al. 2020

Ind. Eng. Chem. Res.

This paper presents a multiobjective mixed-integer nonlinear programming (MOMINLP) model to handle the trade-off issue between improving the heat recovery quantity and quality as well as considering economic feasibility in the integration of an organic Rankine cycle (ORC) with the heat exchanger network (HEN). The first objective is the minimum utility consumption (Q uc) of the stand-alone HEN, after which ORC is constrained upon just absorbing heat below the pinch point of HEN. The second objective is the minimum equivalent thermal resistance (R ex), which represents the higher heat recovery quantity and quality of the HEN–ORC integration. The third objective is the minimum total annual cost (TAC) to ensure economic feasibility. Finally, the optimum working fluid, operating conditions, and the optimum structure for the HEN–ORC integration are obtained. Moreover, a well-studied example is solved to highlight the benefits of the proposed method.

“…As a result, it is essential to accompany data on discharging temperature and temperature lift with specific energy storage capacity and energy storage density. Alternatively, new performance indicators involving exergy [40] and entransy [41] can be defined to assess TES systems, as they contain information about the grade of energy or irreversibility in addition to the amount of energy.…”

Section: Effect Of Magnesium Sulfatementioning

confidence: 99%

A zeolite 13X/magnesium sulfate–water sorption thermal energy storage device for domestic heating

Lemington

Energy Conversion and Management

et al. 2018

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A sorption thermal energy storage (TES) device for domestic heating is presented in this article. The TES device adopts the new design scenario with valve-less adsorber and separate reservoir to eliminate the largediameter vacuum valve for vapor flow, which decreases the cost, reduces the vapor flow resistance, and improves the system reliability. The device is charged by the electric heater, which can add much flexibility to the building energy system as well as contribute to the valley filling and peak shaving from demand side management. The newly developed composite sorbent of zeolite 13X/MgSO4/ENG-TSA (expanded natural graphite treated with sulfuric acid) with the salt mass fraction of 15% in the zeolite 13X/MgSO4 mixture is tested and used in the TES device (denoted as XM15/ENG-TSA). Experimental results show that the TES device with XM15/ENG-TSA has the energy storage density of 120.3 kWh•m −3 at 250°C charging temperature and 25-90°C discharging temperature. The temperature lift is as high as 65-69°C with the adsorption and evaporating temperatures of 25°C. The impregnation of MgSO4 dramatically improves the temperature rising rate during the adsorption heat recovery process, but the specific energy storage capacity of XM15/ENG-TSA is similar to that of zeolite 13X/ENG-TSA. The effect of the impregnated MgSO4 suggests that MgSO4 can be used for low-temperature TES to relieve the self-hindrance of the hydration reaction.