Heat transfer regenerative

Air preheaters employed in power generating plants are either the tubular or regenerative types. Both are periodically washed to remove deposits that accumulate. The frequency of washing is typically once per month however, frequency variations ranging from 5 to 180 washings per year are reported. Many preheaters are sectionalized so that heat transfer areas may be isolated and washed without shutdown of the entire unit. 

An extremely effective means of enhancing heat removal from a reactor is to make use of fluidized-bed technology (3). Heat transfer coefficients for gaseous systems are increased to values of around 600 W/m2K or more by virtue of the very efficient convective-regenerative particle transport mechanism of heat transfer. Further... 

Regenerative Heat Transfer Process for Hydrogen Cyanide Manufacture... 

Desorptive Cooling for Enhanced Regenerative Heat Transfer... 

VOC emissions from printing and chemical plants are oxidized in reverse flow reactors that couple reaction with regenerative heat transfer. The concept here is to maintain a catalyst zone in the center of a packed bed with inert heat-transfer packing on either side. 

A colorless liquid, hydrazine is stable to shock, heat, and cold. The freezing point of hydrazine (34.75°F, 274.9 K) is the highest of commonly used hydrazine-type fuels. Because it starts to decompose at 320°F (433 K) with no catalysts present, it is undesirable for use as the coolant for regenerative cooling of the thrust chamber. Different blends of hydrazine and MMH have been tested to improve heat transfer properties. Hydrazine is generally compatible with stainless steel, nickel, or aluminum. (See Chapter 22 for more information on hydrazine.)... 

In general, the hydrazine-type fuels do not have very good heat transfer properties. Therefore, in the latest development of a high-pressure bipropellant system using N204 and hydrazine-type fuels, the oxidizer N204 has been used as a regenerative coolant instead of the fuel itself. 

Table 4.3a shows the state properties of the ideal regenerative Rankine cycle. Table 4.3b shows the distribution of exergy losses at each process. As seen from this table, the highest exergy loss occurs due to heat transfer in the boiler. 

Example 4.17 Ideal reheat regenerative cycle A steam power plant is using an ideal reheat regenerative Rankine cycle (see Figure 4.23). Steam enters the high-pressure turbine at 9000 kPa and 773.15 K and leaves at 850 kPa. The condenser operates at 10 kPa. Part of the steam is extracted from the turbine at 850 kPa to heat the water in an open heater, where the steam and liquid water from the condenser mix and direct contact heat transfer takes place. The rest of the steam is reheated to 723.15 K, and expanded in the low-pressure turbine section to the condenser pressure. The water is a saturated liquid after passing through the water heater and is at the heater pressure. The work output of the turbine is 75 MW. Determine the work loss at each unit. 

We present here a few examples of eryocooler applications to show where microscale heat transfer issues at low temperatures may be of some concern. The overall size of the eryocooler usually has little bearing on whether microscale heat transfer issues are involved. It is the hydraulic diameter that is important in determining microscale effects. Small hydraulic diameters are required for very effeetive heat exehangers, particularly for those used in high frequency regenerative cryocoolers. For... 

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