Heat distribution

Cracking reactions are endothermic, 1.6—2.8 MJ/kg (700—1200 BTU/lb) of hydrocarbon converted, with heat supplied by firing fuel gas and/or fuel oil in side-wall or floor burners. Side-wall burners usually give uniform heat distribution, but the capacity of each burner is limited (0.1—1 MW) and hence 40 to 200 burners are required in a single furnace. With modem floor burners, also called hearth burners, uniform heat flux distribution can be obtained for coils as high as 10 m, and these are extensively used in newer designs. The capacity of these burners vary considerably (1—10 MW), and hence only a few burners are required. The selection of burners depends on the type of fuel (gas and/or liquid), source of combustion air (ambient, preheated, or gas turbine exhaust), and required NO levels. 

Methods for numerical analyses such as tlris can be obtained from commercial software, and the advent of the computer has considerably eased the work required to obtain numerical values for heat distribution and profiles in a short time, or even continuously if a monitor supplies the boundary values of heat content or temperature during an operation. 

Buried steel pipelines for the transport of gases (at pressures >4 bars) and of crude oil, brine and chemical products must be cathodically protected against corrosion according to technical regulations [1-4], The cathodic protection process is also used to improve the operational safety and economics of gas distribution networks and in long-distance steel pipelines for water and heat distribution. Special measures are necessary in the region of insulated connections in pipelines that transport electrolytically conducting media. 

In static systems, the cooling jackets are normally filled with a glycol and water mixture to provide for uniform heat distribution within the cylinder. This system may be used where the AT of the gas is less than 150°F and discharge gas temperature is less than 190°F. 

Poor heat distribution within llie reactor bed, resulting in hot spots... 

Despite a strong awareness of the potential advantages of district heating in the early nineteenth century, widespread adoption did not occur until technology was developed to handle the numerous problems associated with heat distribution. The Great... 

But problems persisted. The catalyst, moving at rapid rates, tended to disintegrate as it impacted the inside surface of equipment. Dust particles formed, clogging pipes and transfer lines and disrupting the smooth flow of operation. This difficulty in turn prevented uniform heat distribution through the system and affected the rate and extent of both cracking and regeneration. Both the volume and C uality of fuel produced suffered. 

Upward airflow is also practiced. The cable void formed by the raised floor is used to supply air which enters the room via floor grilles. These can be moved to meet the pattern of heat distribution and are normally placed close to the computer cabinets, but consideration must be given to changing air conditions, intended to meet changing room load, entering the computer compartments. Care has to be taken to avoid the updraft lifting dust into the occupied space. 

While the air distribution must match the heat distribution, the position of extracts is not important. Direct return to air-handling units mounted around the room in numbers necessary for reliability is common practice. In the event of loss of one or more cooling modules a well-designed ventilated ceiling adds to reliability by distributing the reduced amount of air in the same proportions throughout the room. 

The short circuiting of furnace gases, resulting in a different heat distribution pattern. 

A periodic problem. We are now interested in the problem of the heat distribution over a uniform thin circlic ring 0 < yj < 27t of radius 7 ... 

Compared with laboratory fixed-bed reactors or conventional extruded monoliths, such a microstructured monolith is smaller in characteristic dimensions, lower in pressure loss by optimized fluid guiding and constructed from the catalytic material solely [3]. The latter aspect also leads to enhanced heat distribution within the micro channels, giving more uniform temperature profiles. 

The two principal methods of dry-heat sterilization are infrared and convection hot air. Infrared rays will sterilize only surfaces. Sterilization of interior portions must rely on conduction. Convection hot-air sterilizers are normally heated electrically and are of two types gravity or mechanical. In gravity convection units, a fan is used to promote uniformity of heat distribution throughout the chamber. 

In the case of heat sterilization processes, the supporting data required include heat distribution and heat penetration studies (usually at least three runs at the minimum process parameters), with calculation of... 

A parametric study was conducted using the Engineering Equation Solver (EES) software. Figure 4 illustrates the variation of the exit temperature of the heat pump (or supply temperature of the heat distribution system) in the heating mode versus COP. Normally, in heating systems, the supply temperature of the heat distribution network plays a key role in terms of exergy loss. This temperature is determined via an optimization procedure. 

Unless there is a specific reason, the supply temperature should be higher in order to increase the exergy efficiency of the heat pumps and hence the overall system, as shown in Figure 82. Other points to be considered in the design include the effect of outdoor conditions on the return temperature of the heat distribution network, the type of users connected to the system, and the characteristics of the heating apparatus. Also, in the heat exchanger... 

Rack ovens have central rack which is rotated around a vertical pivot (Figures 8 and 9). The rack accepts trays of products. The rotating rack evens out the flow of heat to the products. As the rack rotates hot air is blown over the products so that a very even heat distribution is obtained. Some rack ovens are equipped to blow steam over the product, either to give crisp baguettes or to steam products like Christmas puddings. 

Fig. 3.46 shows a cross-section of the sensor head used in the IRT 3000. Heatconcentrating and heat-distributing devices consist of four die-cast zinc parts. 

The position of the pot or pan in the oven could be determined and heat distribution adapted. Dough rounders with better control of many functions could be developed, including the determination of dough viscosity, humidity, color, particle size and some constituents. 

Hot water can be transported over longer distances with little heat loss while steam heat distribution systems can only serve high-density regions. The largest steam system in the United States is a part of New York s Consolidated Edison Company and serves a small part of Manhattan Island. The larger pipes or mains carry 200 to 250°F water under pressure. Re-... 

In situ thermal Injects heat above the water table via Joule heating, radio frequency heating, or means to promote volatilization of contaminants Difficulty in attaining uniform heat distribution... 

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