Flashcards in Principle of Heat Flow Deck (11):

1

## Range

### Tch- Tcc

2

## Approach

### DelT1, delT2

3

## Point temperature difference

### Temperature difference at any point inside the heat exchanger

4

## Average or mixing cup temperature

### Since the temperature the fluid is not uniform inside the system ( hotter near the hot surface and colder close to atmosphere for example) the temperature curves drawn are using the temperature that the fluid would have if mixed perfectly at adiabatic conditions

5

## Important assumptions for fluid flow in a heat exachanger derivation

###
U is constant and independent of temperature

Cp is constant - reason for linear relationship between delT and q

Steady state conditions

Heat transfer with ambient conditions is negligible

6

## Overall heat transfer coefficient

###
May depend upon the area used inside or outside

It does not matter which one we use but we should clearly mention it

7

## Types of flow in heat exchanger

###
Counter current

Parallel

Cross flow

8

## Counter current

###
Most commonly preferred

Constant delT hence almost constant heat transfer throughout

Less heat transfer are compared to other flows

9

## Cross flows

###
Not commonly used

Used in car radiators

Cooling of refrigerator compressor

10

## Parallel flow

###
Not commonly used

High heat transfer area

Usually used when high amount of heat has to be transferred in a short amount of time

Like quenching of hot metal rod

11