ISSN Online: 2377-424X
ISBN Print: 0-89116-559-2
International Heat Transfer Conference 8
DIMENSIONLESS CORRELATION FOR TRANSIENT NATURAL CONVECTIVE HEAT TRANSFER
Abstract
By reducing to non-dimensional forms the equations governing energy and momentum transfer, novel dimensionless groupings of "characteristic" variables, including time, are derived. One of these contains system variables length, temperature rise, time and acceleration
constant, together with fluid properties kinematic
viscosity and expansion coefficient. Another
relates to system heat source thermal capacities.
Taking a ribbon-wound electrical resistor of the short-time rated type used in tap-changers, starters, etc. as an example, a pair of models scaled 2:1 was designed and constructed. These were immersed in transformer oil and heated in the constant current mode for periods of up to 11/2 minutes (well within the transient regime) and temperature rises monitored continuously. The results suggest a useful role for this correlation method where estimates of temperature rises are needed to a greater accuracy than given by the "all heat stored" approximation.
Taking a ribbon-wound electrical resistor of the short-time rated type used in tap-changers, starters, etc. as an example, a pair of models scaled 2:1 was designed and constructed. These were immersed in transformer oil and heated in the constant current mode for periods of up to 11/2 minutes (well within the transient regime) and temperature rises monitored continuously. The results suggest a useful role for this correlation method where estimates of temperature rises are needed to a greater accuracy than given by the "all heat stored" approximation.