Heat exergy analysis

Bjurstrom, H., and B. Carlsson, 1985. An exergy analysis of sensible and latent heat storage, Heat Recovery Syst., 5, 233-250. 

Keywords Latent heat storage exergy analysis, thermoeconomics, economic analysis... 

Ramayya, A.V., and Ramesh, K.N., 1998, Exergy analysis of latent heat storage system with sensible heating and subcooling of PCM, Int. J. Energy Res. 22 411—426. 

Ozgener O., Hepbasli A. (2007). A review on the energy and exergy analysis of solar assisted heat pump systems. Renewable Sustainable Energy Reviews, 11(3), 482-496. 

As some intermediate thermodynamic data are missing or not well known (enthalpy of mixing of CuCl and CuCl2 in HC1/H20 mixtures for example) and some heat exchanges or separation are not linear (for instance, HC1/H20 mixture has an azeotrope which cannot be crossed), we decided to proceed to a global exergy analysis instead of a flow sheet analysis. 

The global exergy analysis shows that the CuCl cycle requires important modifications to become competitive due to problematic separation issues. However multiple variations and simplifications are possible and could help to solve these issues. We have proposed a variation of the cycle, which requires only low temperature heat (below 400°C) and avoids the use of solid phases. 

In this paper, methods to estimate the heat of formation AHj0 and the absolute entropy S° for coal and coal-derived liquids are proposed based on the group contribution method. By applying these methods and the Structured Process Energy-Exergy-flow Diagram (SPEED, 11), an exergy analysis for the H-Coal process is performed. 

Geskin, E. S. and Foster, J., "Exergy Analysis of Fuel Utilization in Heating Furnaces," AIChE National Meeting, Detroit, MI, Aug. (1981). 

Example 4.12 Exergy analysis of a power plant A steam power plant operates on a simple ideal Rankine cycle (see Figure 4.18). The turbine receives steam at 698.15 K and 4200 kPa, while the discharged steam is at 40 kPa. The mass flow rate of steam is 3.0 kg/s. In the boiler, heat is transferred into the steam from a source at 1500 K. In the condenser, heat is discharged to the surroundings at 298 K. Determine the energy dissipated at each state. 

The term Exc is the exergy consumed by the overall processes. We may combine the pinch analysis with the exergy analysis to reduce the number of unit operations and thermodynamic parameters, leading to an optimum operation. The minimum number of heat exchangers needed is obtained by... 

Figure 5.5 is one way of stating the integration problem. In Barclay (1998), the author made an exergy analysis of a combined cycle, combined heat and power installation, based on the real gas turbine of Figure 5.5. It is immediately apparent that the machine needs some alteration to fit a 600 °C MCFC. The operating temperature of the MCFC is related...

A number of items for further improvement of the thermal efficiency is discussed. It requires a systematic exergy analysis. However, any further gain in heat economy has to be traded off against increased capital expenditure and reduced operability. 

Exergy is defined as the maximum amount of work that can be obtained from a material stream, heat stream or work interaction by bringing this stream to environmental conditions. The environmental state is a cmdal concept in exergy analysis. The term environment is regarded as a medium composed of common substances existing in abundance within the Earth s atmosphere, oceans and crust. The reference state is usually taken to be at standard temperature (To = 298.15 K) and pressure (po = 1 atm). Some reference species include CO2,02 and N2, having mole fractions of 0.0003, 0.2099 and 0.7903 in dry air, respectively. 

From electrical conductivity data in Figure 17.12, joule heat caused in CSO—15MFO was estimated to be 8.4 W as shown in Table 17.3. Although further detailed exergy analysis and measurements of actual temperature distribution in the membrane are required, the joule heat caused by oxygen permeation (8.4 W) appears... 

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