Atmospheric air heat exchangers

For the heating of the air, a steam-air heat exchanger is to be used. Its energy load should be sufficient for the heating of the airstream from the initial atmospheric temperature Tq (°C) to the inlet air temperature in the dryer T, and given by the equation... 

Fig. 4. Change of natrolite DTA profile as the K-exchange proceeds (atmosphere air heating rate lOKmin ). The scale on the right indicates the extent of Na K exchange. The arrow points to the endotherm connected with the a (3 metanatrolite transformation (reproduced by permission from [9]...

Decay heat removal loops. The normal route for the removal of decay heat in a fast reactor is via the secondary sodium circuits and the steam plant. Should this route not be available, decay heat in PFR could be rejected by one or more of three thermal syphon loops, each filled with eutectic sodium/potassium alloy. Each loop extracted heat through an immersed coil, intercq>ting some of the primary sodium as it flowed from the core towards an intermediate heat exchanger, and delivered the heat by natural convection to the outside atmosphere through a sodium-potassium/air heat exchanger built into the wall of the secondary containment building. 

Cooldown is provided by the combined exhaust and intake ventilation of the compartments, as well as passively, under natural coolant circulation in the secondary circuit and natural circulation of atmospheric air. The ASEC consists of water-air heat exchangers designed as a system of parallel ribbed pipelines (air convectors) located in separate compartments of the secondary circuit, outside the reactor leak-tight area, at elevations that ensure head for natural circulation sufficient for residual heat removal and reactor cooldown in long-term loss of power. 

Atmospheric corrosion. Air-cooled heat exchangers should not be located where corrosive vapors and fumes from vent stacks will pass through them. 

Tube ventilation In this system cooling tubes which work as heat exchangers are welded between the core packet and the outer frame and are open only to the atmosphere. See to Figures 1.20 (a)-(c). One fan inside the stator, mounted on the rotor shaft, transfers the internal hot air through the tube walls which form the internal closed cooling circuit. A second fan mounted outside at the NDE blows out the internal hot air of the tubes to the atmosphere and replaces it with fresh cool air from the other side. This forms a separate external cooling circuit. 

The theoretical steam rate (sometimes referred to as the water rate) for stream turbines can be determined from Keenan and Keyes or Mollier charts following a constant entropy path. The theoretical steam rate is given as Ib/hr/kw which is easily converted to Ib/hr/hp. One word of caution—in using Keenan and Keyes, steam pressures are given in PSIG. Sea level is the basis. For low steam pressures at high altitudes appropriate coirections must be made. See the section on Pressure Drop Air-Cooled Air Side Heat Exchangers, in this handbook, for the equation to correct atmospheric pressure for altitude. 

Gas turbines can operate in open or closed cycles. In a simple cycle (also known as an open cycle), clean atmospheric air is continuously drawn into the compressor. Energy is added by the combustion of fuel with the air. Products of combustion are expanded through the turbine and exhausted to the atmosphere. In a closed cycle, the working fluid is continuously circulated through the compressor, turbine, and heat exchangers. The disadvantage of the closed cycle (also known as the indirect cycle), and the reason why there are only a few in operation, is the need for an external heating system. That is an expensive addition and lowers efficiency. 

---