Efficiency of heat

A further enhancement to the HRS process whereby the exhaust from a gas fired turbine is used to superheat steam from the HRS process is also possible (129). The superheated steam is then fed through a turbogenerator to produce additional electricity. This increases the efficiency of heat recovery of the turbine exhaust gas. With this arrangement, electric power generation of over 13.6 kW for 1 t/d (15 kW/STPD) is possible. Good general discussions on the sources of heat and the energy balance within a sulfuric acid plant are available (130,131). 

Figure 1. The exergetic efficiency of heat as a function of temperature (reference temperature 0°C).

This remarkable result shows that the efficiency of a Carnot engine is simply related to the ratio of the two absolute temperatures used in the cycle. In normal applications in a power plant, the cold temperature is around room temperature T = 300 K while the hot temperature in a power plant is around T = fiOO K, and thus has an efficiency of 0.5, or 50 percent. This is approximately the maximum efficiency of a typical power plant. The heated steam in a power plant is used to drive a turbine and some such arrangement is used in most heat engines. A Carnot engine operating between 600 K and 300 K must be inefficient, only approximately 50 percent of the heat being converted to work, or the second law of thermodynamics would be violated. The actual efficiency of heat engines must be lower than the Carnot efficiency because they use different thermodynamic cycles and the processes are not reversible. 

The failure of plant by corrosion can be gradual or catastrophic. Gradual failure has few implications for safety providing it is monitored. Direct corrosion-monitoring techniques are described in Section 53.8. Indirectly, the correct interpretation of records relating to metal contamination of products or the loss of efficiency of heat exchangers, etc. can provide useful information. 

Lindquist, S. (1980). Translational efficiency of heat induced messages in Drosophila melanogasler cells. Mol. Biol. 137, 151-158. 

This equation was originally arrived at by the French Engineer Sadi Carnot in 1824 during his investigation on the efficiency of heat engines. In terms of the heat and the entropy changes in the system, the second law may be expressed as follows ... 

The cost of recovery will be reduced if the streams are located conveniently close. The amount of energy that can be recovered will depend on the temperature, flow, heat capacity, and temperature change possible, in each stream. A reasonable temperature driving force must be maintained to keep the exchanger area to a practical size. The most efficient exchanger will be the one in which the shell and tube flows are truly countercurrent. Multiple tube pass exchangers are usually used for practical reasons. With multiple tube passes the flow will be part counter-current and part co-current and temperature crosses can occur, which will reduce the efficiency of heat recovery (see Chapter 12). 

Efficiency of heat recovery to avoid supplementary fuel 492 - 780 = 63%... 

Experiments for verifying the efficiency of heat transfer in the dilute phase were carried out in the equipment shown in Fig. 11 (Kwauk and Tai, 1964). It consisted of two vertical heat transfer columns, i.d. = 300 mm for... 

Based on the similarity of formalin-induced chemical modification between nucleic acids and proteins, the efficiency of heating protocols for DNA/RNA extraction has been demonstrated (see Chapter 3 for detail). Basic AR principle including heating condition and pH value of AR solution as well as certain chemicals may play roles to establish optimal protocols. 

Microwave energy is not transferred primarily by conduction or convection as with conventional heating, but by dielectric loss [28]. The dielectric loss factor (loss factor, e") and the dielectric constant (e ) of a material are two determinants of the efficiency of heat transfer to the sample. Their quotient is the dissipation factor (tan 8),... 

Carbon reinforced products that require less energy to produce and that are ten times stronger than steel, lighter than aluminum, and that conduct more heat than copper can be increasingly used to reduce the weight of vehicles, improve the performance of appliances and tools and increase the efficiency of heat-transfer systems. Other forms of carbon will provide super semiconductors and advanced optics. 

It should be remembered that the actual efficiencies of heat engines and fuel cells are substantially below their... 

Moving bed reactors for oil recovery from shale is one example of this kind of operation. Another somewhat analogous operation is the multistage counterflow reactor, and the four- or five-stage fluidized calciner is a good example of this. In all these operations the efficiency of heat utilization is the main concern. 

Cocurrent and Crosscurrent Plug Flow of Gas and Solids. In cocurrent flow, shown in Fig. 26.9a, all reaction occurs at the feed end, and this represents a poor method of contacting with regard to efficiency of heat utilization and preheating of entering materials. 

The MSSR presents the same advantages as BSCR, such as high efficiency of heat-and mass-transfer and minimal intraparticle diffusional resistance, and are convenient for use in batch processes. For these reasons, the slurry-agitated reactors are also suitable for kinetic studies in the laboratory. Some of their major drawbacks are large power requirement for mechanical agitation,... 

Efficiency of heat pumping—generally decreases with... 

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