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The Log Mean Temperature Difference (LMTD) is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger. Check FAQs
LMTD=(Tho-Tci)-(Thi-Tco)ln(Tho-TciThi-Tco)
LMTD - Log Mean Temperature Difference?Tho - Outlet Temperature of Hot Fluid?Tci - Inlet Temperature of Cold Fluid?Thi - Inlet Temperature of Hot Fluid?Tco - Outlet Temperature of Cold Fluid?

Log Mean Temperature Difference for Counter Current Flow Example

With values
With units
Only example

Here is how the Log Mean Temperature Difference for Counter Current Flow equation looks like with Values.

Here is how the Log Mean Temperature Difference for Counter Current Flow equation looks like with Units.

Here is how the Log Mean Temperature Difference for Counter Current Flow equation looks like.

19.5762Edit=(20Edit-5Edit)-(35Edit-10Edit)ln(20Edit-5Edit35Edit-10Edit)
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Log Mean Temperature Difference for Counter Current Flow Solution

Follow our step by step solution on how to calculate Log Mean Temperature Difference for Counter Current Flow?

FIRST Step Consider the formula
LMTD=(Tho-Tci)-(Thi-Tco)ln(Tho-TciThi-Tco)
Next Step Substitute values of Variables
LMTD=(20K-5K)-(35K-10K)ln(20K-5K35K-10K)
Next Step Prepare to Evaluate
LMTD=(20-5)-(35-10)ln(20-535-10)
Next Step Evaluate
LMTD=19.5761518897122K
LAST Step Rounding Answer
LMTD=19.5762K

Log Mean Temperature Difference for Counter Current Flow Formula Elements

Variables
Functions
Log Mean Temperature Difference
The Log Mean Temperature Difference (LMTD) is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
Symbol: LMTD
Measurement: TemperatureUnit: K
Note: Value should be greater than 0.
Outlet Temperature of Hot Fluid
Outlet Temperature of Hot Fluid is the temperature at which the hot fluid exits the heat exchanger.
Symbol: Tho
Measurement: TemperatureUnit: K
Note: Value should be greater than 0.
Inlet Temperature of Cold Fluid
Inlet Temperature of Cold Fluid is the temperature at which the cold fluid enters the heat exchanger.
Symbol: Tci
Measurement: TemperatureUnit: K
Note: Value should be greater than 0.
Inlet Temperature of Hot Fluid
Inlet Temperature of Hot Fluid is the temperature at which the hot fluid enters the heat exchanger.
Symbol: Thi
Measurement: TemperatureUnit: K
Note: Value should be greater than 0.
Outlet Temperature of Cold Fluid
Outlet Temperature of Cold Fluid is the temperature at which the cold fluid exits the heat exchanger.
Symbol: Tco
Measurement: TemperatureUnit: K
Note: Value should be greater than 0.
ln
The natural logarithm, also known as the logarithm to the base e, is the inverse function of the natural exponential function.
Syntax: ln(Number)

Other Formulas to find Log Mean Temperature Difference

​Go Log Mean Temperature Difference for CoCurrent Flow
LMTD=(Tho-Tco)-(Thi-Tci)ln(Tho-TcoThi-Tci)

Other formulas in Basics of Heat Transfer category

​Go Logarithmic Mean Area of Cylinder
Amean=Ao-Ailn(AoAi)
​Go Heat Transfer Coefficient based on Temperature Difference
hht=qΔTOverall
​Go Hydraulic Radius
rH=AcsP
​Go Equivalent Diameter of Non-Circular Duct
De=4AcsP

How to Evaluate Log Mean Temperature Difference for Counter Current Flow?

Log Mean Temperature Difference for Counter Current Flow evaluator uses Log Mean Temperature Difference = ((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)-(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid))/ln((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)/(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid)) to evaluate the Log Mean Temperature Difference, The Log Mean Temperature Difference for Counter Current Flow in 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. Log Mean Temperature Difference is denoted by LMTD symbol.

How to evaluate Log Mean Temperature Difference for Counter Current Flow using this online evaluator? To use this online evaluator for Log Mean Temperature Difference for Counter Current Flow, enter Outlet Temperature of Hot Fluid (Tho), Inlet Temperature of Cold Fluid (Tci), Inlet Temperature of Hot Fluid (Thi) & Outlet Temperature of Cold Fluid (Tco) and hit the calculate button.

FAQs on Log Mean Temperature Difference for Counter Current Flow

What is the formula to find Log Mean Temperature Difference for Counter Current Flow?
The formula of Log Mean Temperature Difference for Counter Current Flow is expressed as Log Mean Temperature Difference = ((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)-(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid))/ln((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)/(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid)). Here is an example- 19.57615 = ((20-5)-(35-10))/ln((20-5)/(35-10)).
How to calculate Log Mean Temperature Difference for Counter Current Flow?
With Outlet Temperature of Hot Fluid (Tho), Inlet Temperature of Cold Fluid (Tci), Inlet Temperature of Hot Fluid (Thi) & Outlet Temperature of Cold Fluid (Tco) we can find Log Mean Temperature Difference for Counter Current Flow using the formula - Log Mean Temperature Difference = ((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)-(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid))/ln((Outlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid)/(Inlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid)). This formula also uses Natural Logarithm Function function(s).
What are the other ways to Calculate Log Mean Temperature Difference?
Here are the different ways to Calculate Log Mean Temperature Difference-
  • Log Mean Temperature Difference=((Outlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid)-(Inlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid))/ln((Outlet Temperature of Hot Fluid-Outlet Temperature of Cold Fluid)/(Inlet Temperature of Hot Fluid-Inlet Temperature of Cold Fluid))OpenImg
Can the Log Mean Temperature Difference for Counter Current Flow be negative?
No, the Log Mean Temperature Difference for Counter Current Flow, measured in Temperature cannot be negative.
Which unit is used to measure Log Mean Temperature Difference for Counter Current Flow?
Log Mean Temperature Difference for Counter Current Flow is usually measured using the Kelvin[K] for Temperature. Celsius[K], Fahrenheit[K], Rankine[K] are the few other units in which Log Mean Temperature Difference for Counter Current Flow can be measured.
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