Efficiency heat release

In contrast, the use of thicker and less-dense textile structures leads to a delayed and therefore more efficient heat release of the PCM. Furthermore, the phase change temperature range and the application temperature range should correspond in order to realize the desired thermal benefits. 

Table 27-21 gives typical values or ranges of these criteria for gas, oil, and coal. The furnace release rates are important, for they establish maximum local absorption rates within safe hmits. They also have a bearing on completeness of combustion and therefore on efficiency and particulate emissions. Limiting heat release on grates (in stoker firing) will minimize carbon loss, control smoke, ana avoid excessive fly a. ... 

The efficiency, QE, is then defined as the heat absorbed minus the heat released divided by die heat absorbed in the cycle. This expression can, in turn, be transformed to show that the efficiency is equal to tire difference between the two temperarnres of operation, divided by the upper temperamre. 

Reactions occurring in FTS are essentially bond forming, and they release a large amount of heat. This requires an efficient heat removal system. 

GS 11] ]R 5] At high mass flows and with a large heat release, an undesired, substantial temperature increase even for highly efficient micro heat exchanger-reactors is observed (Figure 3.53) [115]. 

As this acid cleavage releases considerable heat, the apparatus used needs efficient heat exchange units [64]. Selectivity of the hydroperoxide cleavage is affected if temperature rises in an undesired manner. For this reason, not the technical 65-90 wt.-% solutions, but rather strongly diluted ones (e.g. below 10%) are employed. In the first case, a sudden loss of the heat exchange function could result in an temperature increase from 50 to 500 °C within seconds. 

The profile shown in Figure 15.21 represents the furnace efficiency, if the casing heat losses are neglected. Making this assumption, the process duty plus the stack loss represents the heat released by the fuel. 

States in 2001 the rate was about 2 kg (4.4 lb) per capita per day, or nearly 208 Tg (229 M short tons) per year. Table 24-4 shows that the composition of miscellaneous refuse is fairly uniform, but size and moisture variations cause major difficulties in efficient, economical disposal. The fuel value of municipal solid wastes is usually sufficient to enable self-supporting combustion, leaving only the incombustible residue and reducing by 90 percent the volume of waste consigned to landfill. The heat released by the combustion of waste can be recovered and utilized, although this is not always economically feasible. 

Legislative restrictions on pollutant emissions have motivated the combustion community to seek new low-emission combustion techniques that are practical industrial energy sources. However, to meet the needs in most industrial applications, a combustion source needs to be able to maintain low-emission output over a range of heat release rates, occupy minimal volume, and have low operating costs per unit energy produced. One would like to maximize the turn-down ratio, volumetric heat release, and overall thermal efficiency while minimizing NOa , CO, and hydrocarbon emission levels. The ultra-low NO, emission performance of the CSC has been previously documented by the authors and its... 

This is frequently the required mode of operation for fast oxidation reactions because the heat release is too fast to provide efficient heat exchange. Most combustion processes are nearly adiabatic (your home furnace and your automobile engine), and many catalytic oxidation processes such as NH3 oxidation in HNO3 synthesis are nearly adiabatic. 

One of the most important considerations in designing a process for converting methanol to olefins was to find the best way to remove the considerable heat of reaction. Despite the fact that we are stopping the reaction at the intermediate olefin product, the reactions leading to these intermediates give off almost 90% of the heat released in the overall MTG reaction scheme (49 vs. 56 kJ/mole of methanol converted for MTO vs. MTG). Efficient removal of the heat of reaction is one of the main reasons a fluid-bed reactor was selected for scale-up demonstration. A second advantage of the fluid-bed is that product composition can be kept constant, since optimum catalyst activity can be maintained by continuous make-up and regeneration. 

A vital constituent of any chemical process that is going to show oscillations or other bifurcations is that of feedback . Some intermediate or product of the chemistry must be able to influence the rate of earlier steps. This may be a positive catalytic process , where the feedback species enhances the rate, or an inhibition through which the reaction is poisoned. This effect may be chemical, arising from the mechanistic involvement of species such as radicals, or thermal, arising because chemical heat released is not lost perfectly efficiently and the consequent temperature rise influences some reaction rate constants. The latter is relatively familiar most chemists are aware of the strong temperature dependence of rate constants through, e.g. the Arrhenius law,... 

Basic specifications on the process are the total heat release (102.86 MBtu/hr), overall thermal efficiency (75%), excess air (25%), the fraction of the heat release that is absorbed in the radiant section (75%), and the heat flux (10,000 Btu/(hr)(sqft). 

Figure 5. Specific heat release as a function of combustion efficiency...

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