Heat pipe tubes

Heat pipe tubes The absorbed heat is transferred by using the heat pipe principle without direct contact to the heat transfer fluid of the solar loop. In this case, there are two different ways of connection (1) the dry connection, where the heat has to be transferred from the condenser through the material of the header tube. This way the installation and removal of the tubes is much easier than with direct flow pipes brazed to the header. On the other hand, heat-conductive paste often has to be used, thus requiring that the pipes be installed professionally and (2) the wet connection, where the fluid of the solar loop directly flows around the condenser of the heat pipes. In this case, no heat-conductive paste is needed, but the exchange of tubes is more difficult. 

Heat/Solvent Recovery. The primary appHcation of heat pipes in the chemical industry is for combustion air preheat on various types of process furnaces which simultaneously increases furnace efficiency and throughput and conserves fuel. Advantages include modular design, isothermal tube temperature eliminating cold corner corrosion, high thermal effectiveness, high reHabiHty and options for removable tubes, alternative materials and arrangements, and replacement or add-on sections for increased performance (see Furnaces, fuel-FIREd). 

Lead—copper alloys are also used as tank linings, tubes for acid mist precipitators, steam heating pipes for sulfuric acid or chromate plating baths, and flashing and sheeting (see Tanks AND pressure vessels). 

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

Fluidized combustion of coal entails the burning of coal particles in a hot fluidized bed of noncombustible particles, usually a mixture of ash and limestone. Once the coal is fed into the bed it is rapidly dispersed throughout the bed as it bums. The bed temperature is controUed by means of heat exchanger tubes. Elutriation is responsible for the removal of the smallest soHd particles and the larger soHd particles are removed through bed drain pipes. To increase combustion efficiency the particles elutriated from the bed are coUected in a cyclone and are either re-injected into the main bed or burned in a separate bed operated at lower fluidizing velocity and higher temperature. 

Fig. 8. (a) Heat pipe showing the use of finned tubing for both heating and cooling and (b), heat pipe exchanger ain heater system. ID = induced draft and... 

Aluminum Heat exchanger tubing, transfer piping... 

Another problem often noticed once the plant is built is incompatibility of materials (heat exchangers, tubing fittings, pipe valves and fittings, etc.) within the purchased secondary systems package with materials in the main plant. Quite often, equipment such as condensers... 

While EVOH is of interest primarily for food packaging applications attention is now being turned to non-food outlets such as automotive fuel tanks, floor heating pipes and toothpaste tubes. 

Normally, heat exchanger tubes are arranged in a staggered manner. The continuous plate is considered as being built up of regular hexagons, with a hole in the center for the pipes. This arrangement is shown in Fig. 9.9. 

Rohren-halter, m. tube (or pipe) holder, tube (or pipe) clamp, -kassie, /. pur ng cassia, -kleuune, /. tube clamp, -kiibler, m. tubular condenser, tube condenser tubular cooler, -libelle, /. spirit level, air level, -lot, n. pipe solder, -manna, /. flake manna, -nudeln, /.pi. macaroni, -ofen, m. tube furnace (for heating tubes liable to explosion) pipe still, -pulver, n. (Expl.) perforated powder, -struktur, /. tubular structure, -substanz, /. (Anat.) medullary substance, -trager, m. tube (or pipe) support, -wachs, n. petroleum ceresin. -werk, n. tubing piping tube mill, -wischer, m. tube brush, -wulst, n. tubular tore, doughnut , -zelle, /. tubular cell, specif. (Bot.) tracheid. 

Figure 10-50C. Tube-side (inside tubes) liquid film heat transfer coefficient for Dowtherm . A fluid inside pipes/tubes, turbulent flow only. Note h= average film coefficient, Btu/hr-ft -°F d = inside tube diameter, in. G = mass velocity, Ib/sec/ft v = fluid velocity, ft/sec k = thermal conductivity, Btu/hr (ft )(°F/ft) n, = viscosity, lb/(hr)(ft) Cp = specific heat, Btu/(lb)(°F). (Used by permission Engineering Manual for Dowtherm Heat Transfer Fluids, 1991. The Dow Chemical Co.)...

When a fluid flows over a stationary or moving surface, the pressure of the fluid decreases along the length of the surface due to friction. This is commonly called the pressure drop of the system. Of particular interest are the pressure drops in pipes (tubes) and in heat exchanger shells. 

Heat pipes. The use of heat pipes involves the incoming cold air stream and the outgoing warm air stream being immediately adjacent and parallel, and between the two is a battery of heat pipes. These contain a liquid and operate on the thermal siphon principle. The liquid takes in latent heat and evaporates and the vapor travels to the cold end of the tube where condensation releases the latent heat. Generally, heat pipes are restricted to 400°C, and effectiveness can be up to 70 per cent. 

A recent development in heat recovery has been the heat tube. This is a sealed metal tube which has been evacuated of air and contains a small quantity of liquid which, for boiler applications, could be water. When heat from the flue gases is applied to one end of the heat pipes the water in the tube boils, turning to steam and absorbing the latent heat of evaporation. The steam travels to the opposite end of the tube which is surrounded by water, where it gives up its latent heat, condenses and returns to the heated end of the tube. Batteries of these tubes can be arranged to form units, usually as a water jacket around a section of a flue. 

We deal here with the stability of flow in a heated capillary tube when liquid is evaporating on the meniscus. The capillary, as shown in Fig. 11.1, is a straight vertical pipe with diameter d and length 1. The wall heat flux is uniform = const. The thermal conditions on the capillary inlet and outlet are ... 

In the past, copper was believed to be toxic to most microbiological species. Although this may be true in a test tube under laboratory conditions, it is not generally true in the real world. In this real world, microbial communities excrete slime layers which tend to sequester the copper ions and prevent their contact with the actual microbial cells, Aus preventing the copper from killing the microbes. Many cases of MIC in copper and copper alloys have been documented, especially of heat-exchange tubes, potable water, and fire protection system piping. 

Values of jf for heat exchanger tubes can be obtained from Figure 12.24 commercial pipes are given in Chapter 5. 

Fluid mechanics. Pump heads, rates, and power piping sizes column tray layout and sizing heat-exchanger tube and shell side bafliing and sizing... 

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