Designing of Heat Exchangers

Water demand from thermal power plants, mainly for steam condensation (power plant cooling) can place a
significant burden on limited local and regional freshwater supplies. An approach to reducing this cooling water
demand is the use of direct dry cooling, which requires no consumptive water use and can reduce a power plants
water demand by up to95 percent. Direct dry cooling uses air‐cooled steam condensers which consist of a series of
finned, air‐cooled condenser tubes arranged in an A‐frame configuration. Steam is routed from the steam turbine to
the condenser, where the heat from the condensing steam is rejected to the environment via the finned tubes. Beneath
these condenser tubes is an array of fans, which force a stream of air through the condenser. A major limitation to
using this cooling technology is that air‐cooled steam condensers are unable to maintain their performance during
very hot and/or windy periods. This directly affects energy production because a reduction in condenser performance
creates backpressure on the steam turbine and reduces electricity generation. Growing demand for water for both
domestic and industrial use has brought an increased interest in use of Air Cooled condensers. A steam condenser is
a heat exchanger that converts steam from its gaseous state into liquid form by operating at a pressure lower than
that of the surrounding atmosphere. Steam condensers are used in various industries, with key sectors including:
Power sector, Refineries, Marine and Chemical processing.
In the power sector, steam is used to generate electricity. Oil, coal, gas, nuclear, biomass, and solar thermal power
generation methods all use steam to create energy. A steam turbine is used for generating mechanical power in a
rotary motion, and is powered by the extraction of thermal energy from pressurized steam, which is produced from
water or other liquids. Steam power plants across the globe operate on the standard known as the Rankine Cycle.
This cycle consists of four main components: boiler, turbine, steam condenser, and pump. In a simple steam turbine
based power plant, water enters a pump, where it is compressed at high pressure – step one in figure three – and then
this compressed water passes through the boiler, as can be seen in step two. In the boiler, water is heated by burning
fuel, and is converted into steam. This superheated, highly pressurized steam then enters the steam turbine, where it
expands to rotate the turbine shaft, thereby generating electricity (step three). Steam from the turbine then enters the
steam condenser, where it is condensed back into water (step four). This saturated water then enters the pump to
restart the cycle. Steam condensers are also used in Integrated Gasification Combined Cycle (IGCC) and Combined
Cycle Gas Turbine (CCGT) power plants that use steam turbines, to reuse the water in the cycle

Objective of this review paper reviews the literatures related to the parallel and counter flow of different types of heat exchangers and modifications made to improve the performance. Various papers were reviewed from those papers what are the developments in parallel and counter flow heat exchanger are summarized. The development of any system is need because it helps to optimize, improve performance or reduce the cost of system. The heat exchanger development did by many researchers using software's, design methods, changing the designs, changing shape of tubes, applying second law of thermodynamics etc. The fluid velocity, Reynolds number, overall heat transfer coefficient, baffle spacing, number of baffles, pressure drop, LMTD, helix angle of tubes plays very important role in heat exchanger performance.

Heat exchanger is one of the important devices in cooling and heating process in Factories, buildings, transports and others. The heat exchanger is found in large Construction to support cooling process such as fossil fuel power plant. In the present study, heat transfer from hot water to cold water by double pipe heat exchanger consists concentric tube is experimentally investigated. The horizontal double pipe heat exchanger is made from Galvanised iron tube with inner tube and outer tube. The inner tube is consists of 26mm internal & 34 mm outer diameter. The outer tube is consisting of 68 mm internal & 76 mm outer diameter. A set of the experiments were carried out to investigate for counter flow & parallel flow to determine heat transfer coefficient in a double pipe heat exchanger.