A switching relay in which a small heater warms a bimetal element which bends to provide the switching force.

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The shell or cylinder is usually made of close-grained cast iron, with surfaces machined as required. Gunmetal or fabricated steel may be used as alternatives depending upon requirements. Inspection doors are fitted in the distribution belts. End boxes with end access covers are of the same material as the shell. Sacrificial anodes in the rod or plug form and an electrical contract strip are fitted to minimize corrosion.

The tube stack is made up of stress-relieved aluminum brass tubes expanded into Naval brass tube plates, one plate is fixed as shown and the other is free to allow for expansion of the stack. Brass circular baffles give radial flow to the fluid and support to the tube stack.

In recent designs of tube-type heaters, the guided flow concept has been introduced, i.e. a secondary heating, or cooling, surface in the form of radial fins integral with the tubes between which flow is guided radially, alternately out and in from section to section. This gives (1) greater heat transfer surface (2) better heat transfer (3) lower metal surface temperature (4) in the case of oil heaters less risk of oil cracking and hence fouling.

Shell and Tube Heat Exchanger


1. A unit operation based on heat transfer which functions in the tube heater. give off heat. heat exchanger. 2. An electric heating element for supplying heat to an indirectly heated cathode in an electron tube.


In an extraction turbine, steam is withdrawn from one or more stages, at one or more pressures, for heating, plant process, or feedwater heater needs. They are often called 'bleeder turbines'.


The part of a process heater into which the burners fire. Tubes mounted in this area of the furnace receive heat principally via direct radiation from both burner flames and furnace refractory. Physical volume arrangement of the radiant section has a great effect on burner choice and required flame patterns.


A device using highly superheated steam or high-temperature flue gases as a medium serving to restore superheat to partly expanded steam; used often between high- and low-pressure turbines.


A type of feedwater heater operating with water and steam in direct contact. It is designed to heat the water and drive off oxygen.


A heater with electric resistance, steam, or hot water heating elements to heat the air. Natural or forced draft units are designed for wall mounting.


In this type of heater a steam used to heat the air flow. The heater consists of set of heating banks. Each bank contains has multiple of U-tubes with extended surface fins for passing a steam.


In a water tube marine boiler, tubes that protect the super heater tubes from the fire of combustion.


A heater that has a set of heat-transfer coils through which air is forced by a fan operating at a relatively high velocity.

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