Water heat-exchange

Condensable hydrocarbon components are usually removed from gas to avoid liquid drop out in pipelines, or to recover valuable natural gas liquids where there is no facility for gas export. Cooling to ambient conditions can be achieved by air or water heat exchange, or to sub zero temperatures by gas expansion or refrigeration. Many other processes such as compression and absorption also work more efficiently at low temperatures. 

Fig. 8. Combustion turbines with process heat recovery (a) represents direct use of exhaust gas for process heating where industrial process includes refinery, chemicals, food processing, and ethanol production and (b) exhaust-to-water heat exchanger where industrial process includes material drying,...

Fire or explosion hazards require special motor enclosures. Hazards include combustible gases and vapors such as gasoline dust such as coal, flour, or metals that can explode when suspended in air and fibers such as textile lint. The land of motor enclosure used depends on the type of hazard, the type and size of motor, and the probability of a hazardous condition occurring. Some available enclosures are explosionproof motors, which can withstand an internal explosion force-ventilated motors cooled with air from a safe location and totallv enclosed motors cooled bv air-to-water heat exchangers and pressurized with safe air, instrument air, or inert gas,... 

Specimen Location Closed-cycle service water heat exchanger (turbine cooling)... 

Heat exchangers with flowing cold electrolyte in fresh-water heat pump reservoirs must be treated similarly [9]. Here the cold electrolyte circuit need not have expensive insulated bushings installed as shown in Fig. 20-3, and the entire water pump equipment does not have to be grounded but must be covered to prevent contact. Electrical separation as in Fig. 20-3 is only undertaken with hot-water heat exchangers. 

Inert gas-filled motors can also be used in refineries and chemical plants, but their applications are limited. They have tightly fitted covers and oil seals around the shaft to minimize gas leakage, are continually pressurized with an inert gas or instrument air, and are equipped with an internal air-to-water heat exchanger. Inert gas-filled motors are suitable for any hazardous location but require auxiliaries such as cooling water, gas pressurizing system, and control accessories. 

Flue economizers include small auxiliary air-to-water heat exchangers that are installed in the flue pipe. The unit captures and recycles the usable heat that is usually lost up the flue. The recaptured heat is used to prewarm water as it returns from the distribution system. If the flue temperature is lowered too much, moisture, corrosion and freezing may occur in the flue pipe. Depending upon the age and design of the boiler and burner, a flue economizer can provide annual fuel savings of 10 to 20% and a payback of 2 to 5 years. 

There are various types of cooling water heat exchangers to be found in use today, and the permutations of these may number almost as many as the applications in which they are employed. Jackets on chemical reaction vessels are a specific type of heat exchanger, as are the coil bundles in evaporative condensers, plate and frame and shell and tube heat exchangers. 

Hot water heat exchanger. In this H/Ex., heat contained in some of the refrigerant vapor from the first stage generator is transferred to a two pipe, closed loop, hot water heating circuit. 

Figure 13. Water/SS "vapour-dynamic" thermosyphon 1-electric heater 2-boiler 3-condenser 4-feeding liquid tube 5-vapour passage 6-trap for NCG (on the top of additional condenser) 7- water heat exchanger a - water b -vapour c - NCG.

Water-to-water heat exchanger Finned-tube heat exchanger, water in 150-300 850-1700... 

Figure 6.26 Longtitudinal section of a Group II pressurized squirrel cage motor with vertical axis, indicating the internal protective gas circulation for cooling via gas/ water heat exchangers (one shown at the left side).

Generator-Type of protection EEx p II T2 Protective gas air Operational mode leakage compensation Rated power 1050 kVA, 840 kW Rated voltage 400 V 3 AC Rated frequency 50 cps Rated speed 1000 min-1 Cooling air/water heat exchanger... 

SOLUTION A waler-to-water heat exchanger is to be installed to transfer energy from drained hot v/ater to the incoming cold water to preheat it. The rate of heat transfer in the heat exchanger and the amounts of energy and money saved per year are to be determined. 

A cross-flow air-to-water heat exchanger with an effectiveness of 0.65 is used to heat water (Cp = 4180 J/kg °C) with hot air = lOiO J/kg °C). Water enters the heal exchanger at 20°C at a rate of 4 kg/s, while air enters at 100°C at a rale of 9 kg/s. If the overall heat transfer coefficient based on the water side is 260 W/m °C, determine the heal transfer surface area of the heat exchanger on the water side. Assume both fluids are unmixed. An.wcr 6 .4... 

In a parallel-flow, water-to-water heat exchanger, the hot water enters at 75 0 at a rate of 1.2 kg/s and cold water enters at 20 0 at a rate of 0 9 kg/s. The overall heat transfer coefficient and the surface area for this heal exchanger are 750 W/m °C and 6.4 m , respectively, The specific heat for both the hoi and cold fluid may be taken to be 4,18 kJ/kg 0. For the same overall heat transfer coefficient and the surface area, the increase in the effectiveness of this heal exchanger if counter-flow arrangement is used is... 

With double tube gas to water heat exchanger. Cooling water within manufacturer s standard conditions of temperature and pressure. 

Another problem peculiar to the application of a sodium-to-water heat exchanger system in a nuclear power plant is the reactor safeguards considerations of a possible leak. In certain reactors, the introduction of hydrogen or its compounds can cause serious control difficulties. Therefore, it is necessary to ensure that a direct leak of water-to-reactor coolant is virtually impossible. 

Some types of equipment require production tests , type tests , performance tests , routine tests , abbreviated tests or special tests , or a combination of these tests. The subtitles are sometimes used with different meanings. Production tests are required for complex equipment such as high-voltage generators and motors, and these tests are performed in the factory before the complete unit is assembled. For example the rotors are balanced without the stator, air-to-water heat exchanges can be tested to withstand hydraulic pressure, winding insulation and individual coil insulation can be tested. 

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