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Heat Transfer

Heat Transfer through Composite Walls


This apparatus enables the student to study the characteristics of composite structures and its heat transfer ability across the composite walls by altering the combination of slabs. The apparatus consists of three slabs of different materials of same thickness. The slabs are brought together in contact. The three slabs are brass, M.S and asbestos. One surface of the slab is electrically heated and the other end is cooled, .the temperatures of the slabs are measured using thermocouples and are indicated by temperature indicator. The power Input to the heater is measured by Voltmeter and Ammeter.


Condensation in Drop wise & Film Wise Forms


Condensation plays a significant role in the heat rejection parts of the Rankine power cycle and the vapor compression refrigeration cycle, which generally involve pure substances. Dehumidication in air conditioning and the production of liquefied petroleum gases, liquid nitrogen and liquid oxygen and examples in which condensation in a mixture takes place. Condensation on cooled surface occurs in one of two ways: Film or Drop wise condensation.


Emmissivity Measurement Apparatus
This system is designed to study the thermal radiation of a given two identical specimen (made out of homogeneous material) one with black coating and other without coating. This system helps students to study the emmisivity of non-black surface during the charge. The setup consists of two circular brass plates identical in size and is provided with heating coils at the bottom. One of the brass plates is coated black in colour, which is called black body and the other gray body. The plates are mounted on asbestos cement sheet and surrounded by a wooden enclosure so as to provide undisturbed natural convection surroundings. The heat input to the heater is varied by Variac and is measured by Ammeter & Voltmeter. A temperature indicator with a selector switch is provided to measure the various temperatures of the specimen


Heat Transfer in Forced Convection Apparatus
This system is designed to study the thermal radiation of a given two identical specimen (made out of homogeneous material) one with black coating and other without coating. This system helps students to study the emmisivity of non-black surface during the charge. The setup consists of two circular brass plates identical in size and is provided with heating coils at the bottom. One of the brass plates is coated black in colour, which is called black body and the other gray body. The plates are mounted on asbestos cement sheet and surrounded by a wooden enclosure so as to provide undisturbed natural convection surroundings. The heat input to the heater is varied by Variac and is measured by Ammeter & Voltmeter. A temperature indicator with a selector switch is provided to measure the various temperatures of the specimen


Thermal Conductivity of Insulating Powder


The apparatus consists of two concentric copper spheres made out of copper. A heating coil is provided in the inner sphere. The empty space between the inner and outer spheres are filled with insulting powder whose thermal conductivity is to be determined. The heat input o the heater can be varied using a variac provided on the panel. Necessary thermocouples are provided in the setup to study the thermal conductivity of insulating powder. 


Heat Transfer in Lagged Pipe Apparatus


The apparatus consists of a metal pipe with two layers of insulation. An electric heating coil wound on a silica rod is placed at the centre. The ends are thickly insulated to prevent heat loss so that, heat flow only in a radial direction. Three thermocouples each are placed at different radii to measure the temperature distribution within the cylinder.


Heat Transfer in Natural Convection


Convection heat transfer occurs by the movement of fluid particles. If the motion of fluid particles occurs by the variation of density of the fluid due to temperature difference, then the heat transfer process is called free or natural convection.
The apparatus consists of a vertical stainless steel tube enclosed in a rectangular duct; front side of the duct is made of transparent section to facilitate visual observation. An electrical heating element embedded in a copper tube acts as the heat source. The surface temperature is measured at different heights using thermocouples. The surface of the tube is polished to minimize radiation losses. A voltmeter and an ammeter enable the determination of wattage dissipated by the heater.


Parallel Flow /Counter Flow Heat Exchanger


The apparatus consists of a concentric tube heat exchanger. The hot fluid (Hot water) is obtained from an electric geyser and it is made to flow through the inner tube. The cold fluid (cold or ambient temperature water) is made to flow through the outer tube. When the cold fluid and the hot fluid is made to pass in the same direction, the process is called parallel flow, when the cold fluid and the hot fluid is made to flow in opposite direction the process is called counter flow. Temperatures at the inlet and outlet of the fluids are measured using thermocouples and are connected to a digital temperature indicator.


Shell and Tube Heat Exchanger


This equipment allows student to fully investigate the performance and characteristic of a shell and multi tube heat exchanger. It consists of 12 tubes of 12mm outside diameter and the effective length of the tube is 500mm with two tube pass. The shell is made of stainless steel having inside diameter of 150mm with 6 segmental baffles. The water flow rate is measured using a rotameter. Thermocouples are provided for measuring the inlet and outlet temperature hot and cold fluids.


Stefan Boltzman Apparatus


This apparatus is designed to determine Stefan Boltzman constant for radiation heat transfer. The apparatus consists of a flanged copper hemisphere fixed on a flat non-conducting plate. A test disc made of copper is fixed to the plate, thus the test disc is completely enclosed by the hemisphere. The outer surface of the hemisphere is enclosed in a vertical water jacket used to heat the hemisphere to a suitable constant temperature. Three Cr-Al type thermocouples are attached at three strategic places on the surface of the hemisphere to obtain the temperatures. The disc is mounted on a bakelite sleeve which is fitted in a hole drilled at the centre of the base plate. Another Cr-Al thermocouple is fixed to the disc to record its temperature


Thermal Conductivity of Solids by Guarded Hot Plate Method

This equipment allows student to determine the thermal conductivity of a poor conducting material, like asbestos sheet by guarded hot plate method. The test specimen is placed on a flat plate heater assembly consisting of an electrically heated inner plate (main heater) surrounded by a guard heater. The guard heater is carefully controlled to maintain the same temperature on both sides of the gap separating the main and the guard heaters. This prevents lateral heat flow from the main heater and ensures that all heat energy flows in the direction of the specimen. On the opposite side of the specimen are additional flat plate heaters (the "cold" plate) that are controlled at a fixed temperature selected by the operator. For a given heat input to the main heater, the hot plate assembly rises in temperature until the system reaches equilibrium. The final hot plate temperature depends on the electrical power input, the thermal resistance of the specimen, and the temperature of the cold plate. The average thermal conductivity, k, of the specimen is determined from the Fourier heat flow equation:


Thermal Conductivity of Liquid


This equipment allows student to determine the thermal conductivity of a poor conducting liquid, like liquid glycerin. All the heat transfer experimental setup is of single unit, consists of a Powder Coated M.S Panel


Thermal Conductivity of Metal Bar


The apparatus consists of a metal bar; one end of the metal bar is heated by an electric heating coil while the other end projects inside the cooling water jacket. The middle portion of the rod is surrounded by an insulating material like asbestos to minimize lateral heat transfer from the rod and thus ensure a more nearly constant temperature gradient throughout the length of the rod. The temperature of the bar is measured at five different locations while the radial temperature distribution is measured separate thermocouples at two different sections in the insulating shell. The heater is provided with a dimmer stat for controlling the heat input, water can be circulated through the jacket and its flow rate and temperature rise can be noted down.

 
     
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