Thick fluids such as asphalt and waxes and thepipes in which they flow are often heated in order to reducethe viscosity of the fluids and thus to reduce the pumpingcosts. Consider the flow of such a fluid through a100-m-long pipe of outer diameter 30 cm in calm ambientair at 0°C. The pipe is heated electrically, and a thermostatkeeps the outer surface temperature of the pipe constant at25°C. The emissivity of the outer surface of the pipe is 0.8,and the effective sky temperature is -30°C. Determine thepower rating of the electric resistance heater, in kW, thatneeds to be used. Also, determine the cost of electricityassociated with heating the pipe during a 10-h period underthe above conditions if the price of electricity is $0.09/kWh.
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
Thick fluids such as asphalt and waxes and the
pipes in which they flow are often heated in order to reduce
the viscosity of the fluids and thus to reduce the pumping
costs. Consider the flow of such a fluid through a
100-m-long pipe of outer diameter 30 cm in calm ambient
air at 0°C. The pipe is heated electrically, and a thermostat
keeps the outer surface temperature of the pipe constant at
25°C. The emissivity of the outer surface of the pipe is 0.8,
and the effective sky temperature is -30°C. Determine the
power rating of the electric resistance heater, in kW, that
needs to be used. Also, determine the cost of electricity
associated with heating the pipe during a 10-h period under
the above conditions if the price of electricity is $0.09/kWh.
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