Condensation heat pipes

A second property, closely related to the first, is the abiHty of the heat pipe to effect heat-flux transformation. As long as the total heat flow is ia equiHbrium, the fluid streams connecting the evaporatiag and condensing regions essentially are unaffected by the local power densities ia these two... 

The special forms consist of the many types of anode which are used for protecting smaller containers. Boilers, heat exchangers and condensers belong to this group. Besides the rod anodes already mentioned with tube screw joints which can be screwed into the container from outside, there are also short and round anode supports as well as more or less flat ball segments which are bolted onto the protected surface with cast-on supports. These shapes are mostly manufactured from magnesium alloys. In addition, there are star-shaped or circular anodes for installation in condensers and pipes. The weight of these anodes lies between 0.1 and 1 kg. 

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. 

Where it is available the source can be a separate boiler plant, but common practice is to employ purpose-made electrode boilers within or adjacent to the plant. The latter reduces sensible gains to the plant but, being essentially saturated steam, condensate return pipes are required. In addition to the rise in moisture content of the air (kg/kg) being dependent on airflow and steam-injection rates, there is a very small increase in dry bulb temperature by the cooling of the vapor to the air temperature. The rise in total heat is total heat of steam (kJ/kg) x quantity supplied per kg air. 

Depending on the end use of the compressed air, some or all of the condenser heat can be used to re-heat the cold air. This maybe necessary in winter, when distribution piping could be colder than the evaporator. When the air is released through a power tool, the final condition maybe less than 5% saturation. 

Heat pipes between the two ducts. These comprise a coil made with closed pipes, filled with a volatile liquid. This liquid will condense in one coil and evaporate in the other, at the same pressure and therefore at the same temperature. 

Obrecht, Malvern F. PhD. Steam and Condensate Return Line Corrosion. Factors That Accelerate It, Retard Tt, with Emphasis on Oxygen. Heating, Piping Air Conditioning, USA, August 1964. 

Recovery column condenser double-pipe, heat transfer area 1.5 m2, design pressure 2 bar, materials carbon steel. 

Condensate drainage devices, 70 148 Condensate polishing ion exchange in, 74 417 in steam-generating systems, 23 227 water softening method for, 26 122-123 Condensate return, in heat pipes, 73 226 Condensate return systems, 70 147-148 Condensate systems, in industrial water treatment, 26 136-137 Condensation, 9 281-282. See also Polycondensation control of VOCs by, 26 679-680 ketone, 74 570... 

The heat pipe achieves its high performance through the process of vapor state heat transfer. A volatile liquid employed as the heat-transfer medium absorbs its latent heat of vaporization in the evaporator (input) area. The vapor thus formed moves to the heat output area, where condensation takes place. Energy is stored in the vapor at the input and released at the condenser. The liquid is selected to have a substantial vapor pressure, generally greater than 2.7 kPa (20 mm Hg), at the minimum desired operating temperature. The highest possible latent heat of vaporization is desirable to achieve maximum heat transfer and temperature uniformity with minimum vapor mass flow. 

A very important feature of heat pipe (HP) is the ability to transport a large amounts of energy over the length of heat pipe with a small temperature drop by means of liquid evaporation at the heat pipe evaporator (heat source) and vapour condensation at the condenser (heat sink) and liquid movement in the opposite direction inside a wick by capillary force. Essential is a possibility to change the direction of a heat flow along the heat pipe in time and to use heat pipes for cooling and heating alternatively. 

In our experiments as an experimental set-up an aluminium multi-channel panel was chosen. The main parameters of flat aluminium heat pipe panel, developed in the Luikov Institute are HPP width -70mm, HPP height - 7 mm, HPP length - 700 mm, evaporator length - 98 mm, condenser length - 500 mm, mass- 0, 43 kg. Propane was applied to fill the HPP and it is interesting as a working fluid with the point of view of its compatibility with all heat pipe envelopes and wick materials (aluminium, steel, stainless steel, copper, AL2 O3, etc). 

The cooling water (or other medium) must absorb enough heat to balance the heat of vaporization and condensate subcooling. Piping and hot wells must be sized based upon the maximum condenser requirement. The following example illustrates the method of calculating the quantity of cooling water for a specific service. 

The basic design of a heat pipe may be modified to operate as a temperature-control device, as shown in Fig. 12-21. A reservoir containing a noncondensible gas is connected to the heat-removal end of the heat pipe. This gas may then form an interface with the vapor and choke off part of the condensation to the wick. With increased heat addition, more vapor is generated with an increase in vapor pressure, and the noncondensible gas is forced back into the reservoir, thereby opening up additional condenser area to remove the additional heat. For a reduction in heat addition, just the reverse operation is... 

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