LATENT HEAT was discovered by Scottish physician and chemist JOSEPH BLACK
He was born on 16th April 1728.
He was a professor of Anatomy and Chemistry at the University of Glasgow for 10 years from 1756, and then Professor of Medicine and Chemistry at the University of Edinburgh from 1766, teaching and lecturing there for more than 30 years.
In 1761 he deduced that the application of heat to ice at its melting point does not cause a rise in temperature of the ice/water mixture, but rather an increase in the amount of water in the mixture.
JOSEPH Black's theory of latent heat was one of his more-important scientific contributions.
The theory of latent heat marks the beginning of thermodynamics.
He also showed that different substances have different specific heats.
The theory ultimately proved important not only in the development of abstract science but in the development of the steam engine.
The latent heat of water is large compared with many other liquids, so giving impetus to James Watt's attempts to improve the efficiency of the steam engine invented by Thomas Newcomen.
Joseph Black and Watt became friends after meeting around 1757 while both were at Glasgow. Black provided significant financing and other support for Watt's early research in steam power.
He died peacefully at his home in Edinburgh in 6th December 1799. The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after Black.
Joseph Black lived for 71 years in this planet.
Even today he lives in the form of latent heat and carbon dioxide.
PROBLEM – 01
The following data relate to a three phase arc furnace:
Quantity of steel to be melted in one hour = 5 tons
Specific heat of steel = 0.5kJ/kg-degree centigrade
Latent heat of steel 37.3 kJ/kg
Melting point of steel = 1370 degree centigrade
Initial temperature of steel = 20 degree centigrade
Overall efficiency = 60 percentage
Input current = 5700 A
Resistance of transformer referred to secondary = 0.008 ohms
Reactance of transformer referred to secondary = 0.014 ohms.
Determine the following:
1. Average kW input to the furnace
2. Arc voltage
3. Arc resistance
4. Power factor of the current drawn from the supply and
5. Average kVA input to the furnace.
The following data relate to a three phase arc furnace:
Quantity of steel to be melted in one hour = 5 tons
Specific heat of steel = 0.5kJ/kg-degree centigrade
Latent heat of steel 37.3 kJ/kg
Melting point of steel = 1370 degree centigrade
Initial temperature of steel = 20 degree centigrade
Overall efficiency = 60 percentage
Input current = 5700 A
Resistance of transformer referred to secondary = 0.008 ohms
Reactance of transformer referred to secondary = 0.014 ohms.
Determine the following:
1. Average kW input to the furnace
2. Arc voltage
3. Arc resistance
4. Power factor of the current drawn from the supply and
5. Average kVA input to the furnace.
PROBLEM – 02
The following data relate to a three phase arc furnace:
1. Current drawn = 4000 A
2. Arc voltage = 60 V
3. Resistance of the transformer referred to secondary = 0.0025 ohms
4. Reactance of the transformer referred to secondary = 0.005 ohms
Calculate the following
1. Power factor and KW drawn from the supply.
2. If the overall efficiency of the furnace is 70 percent, find the time required to melt 3 ton of steel.
The latent heat of steel = 37.2 kJ/kg
Specific heat of steel = 0.5 kJ/kg.K
Melting point of steel - 1370 degree centigrade and
Initial temperature of steel = 20 degree centigrade
The following data relate to a three phase arc furnace:
1. Current drawn = 4000 A
2. Arc voltage = 60 V
3. Resistance of the transformer referred to secondary = 0.0025 ohms
4. Reactance of the transformer referred to secondary = 0.005 ohms
Calculate the following
1. Power factor and KW drawn from the supply.
2. If the overall efficiency of the furnace is 70 percent, find the time required to melt 3 ton of steel.
The latent heat of steel = 37.2 kJ/kg
Specific heat of steel = 0.5 kJ/kg.K
Melting point of steel - 1370 degree centigrade and
Initial temperature of steel = 20 degree centigrade
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