Heat-transfer fluids, metallic containment

Standard Practices for Simulated Service Testing for Corrosion of Metallic Containment Materials for Use With Heat-Transfer Fluids in Solar Heating and Cooling Systems Standard Test Method for Corrosion of Steel by Sprayed Fire-Resistive Material (SFRM) Applied to Structural Members... 

Indirect fluid heater Very useful for high-pressure or corrosive fluids where special metallurgy (i.e., corrosion-resistant metals) can be used in smaller, less costly containment than traditional shellside boiling. Heating medium (steam/ dowtherm/electric, etc.) heats an intermediate bath of water/NH3/Therminol or similar heat-transfer fluid that then heats a second coil at much lower cost than shellside heating or boiling. (See Fig. V-8.)... 

The major technical barrier associated with biomass combustion systems is the formation of tenacious deposits on heat transfer surfaces caused by the unique high-temperature chemistry of biomass ash. Many types of biomass used in combustion systems contain alkali metal species sodium, potassium, and calcium. The ash content of woody biomass is quite low and not a problem. The ash content of agricultural residues such as wheat straw, rice straw, com stover, and alfalfa stems can be quite high, on the order of 5 percent or up to 20 percent for rice straw and rice husks. The presence of alkali metals in conjunction with the high silica content of some biomass ashes can lead to molten ash at combustion temperatures.553-658 In some cases, the K, Si, and A1 contents are such that very low melting-point eutectic mixtures can form. The materials can be fluid at combustion temperatures, but form glasslike deposits on colder downstream surfaces such as heat exchanger tubes. 

One must remember that nothing happens to the parts alone. These cleaning steps are applied to the parts and the basket in which they are contained. If the basket blocks fluid flow because it has too small an open area, the parts won t be well contacted with solvent. If it has a thermal mass approaching that of the parts, hot solvent vapor will condense on its surfaces instead of those of the parts. This is why it is important to choose a parts basket which has these two characteristics (1) small (thin) support elements so the open area is as large as possible to not block fluid flow, and (2) as little metal as possible to minimize thermal mass so that heat transfer potential is not wasted (in Box 1.4 is described a situation where the opposite is desired). These characteristics minimize loss of the treatment effect by not "wasting" it on the parts basket. 

In case of cooling problems the fuel salt and the fluid containing FPs (salt or metal) of the gas processing unit can be drained into a subcritical tank located in a water pool. For instance, a large amount of water is used as a decay heat thermal buffer so as to reduce the heat to cold sink transfer rate need by a factor 10. This heat transfer is achieved by passive thermos siphons or heat pipes to the atmosphere through the reactor budding walls (the third barrier). If unattended for a very long time, then the fuel salt will solidify. 

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