Q = UA (LMTD) shows the rate of heat transfer across a finite temperature difference between 2 surfaces or fluids for a given surface area. Q = UA (LMTD) shows the rate of heat transfer across a finite temperature difference between 2 surfaces or fluids for a given surface area.
What do you mean by LMTD & NTU method?
The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD).
Why we use log mean temperature difference?
The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The use of the LMTD arises, straightforwardly, from the analysis of a heat exchanger with constant flow rate and fluid thermal properties.
What is log mean temperature difference used for?
heat transfer
1. The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
What is log mean temperature difference in a heat exchanger?
The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
What is the difference between LMTD and e NTU method?
The LMTD method is convenient for determining the overall heat transfer coefficient based on the measured inlet and outlet fluid temperatures. The ε-NTU method is more convenient for prediction of the outlet fluid temperatures if the heat transfer coefficient and the inlet temperatures are known.
Can log mean temperature difference be negative?
In particular, if the LMTD were to be applied on a transient in which, for a brief time, the temperature difference had different signs on the two sides of the exchanger, the argument to the logarithm function would be negative, which is not allowable.
Why do we use log mean temperature difference instead of mean temperature difference?
How to calculate logarithmic mean?
Choose a number very close to the original number that you can construct using factors whose logarithms you have learnt.
What is logarithmic mean temperature difference?
Logarithmic mean temperature difference. The logarithmic mean temperature difference (also known as log mean temperature difference or simply by its initialism LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers.
What is a temperature log?
A temperature log is a document in which information about temperatures is maintained. The log usually consists of temperature readings taken at set intervals over a given period of time.
What is the equation for temperature?
Equation for Specific Heat. You can use the property of specific heat to find a substance’s initial temperature. The equation for specific heat is usually written: Q = mcΔT. where Q is the amount of heat energy added, m is the substance’s mass, c is specific heat, a constant, and ΔT means “change in temperature.”.
