HEAT TRANSFER

Question 1

measure of the amount of energy possessed by the molecules of a substance

Answer 1

TEMPERATURE (T)

Question 2

transfer of energy as heat occurs at the molecular level as a result of a temperature difference

Answer 2

HEAT (Q)

Question 3

transfer of energy resulting from a force acting thru a distance

Answer 3

WORK (W)

Question 4

heat transfer by the interactions of atoms or molecules of a material

Answer 4

CONDUCTION

Question 5

heat transfer by the mixing and motion of macroscopic portions of a fluid

Answer 5

CONVECTION

Question 6

heat transfer by electromagnetic radiation that arises due to the temp. of a body

Answer 6

RADIATION (Radiant Heat Transfer)

Question 7

heat transfer rate per unit area (Q/A)

Answer 7

HEAT FLUX

Question 8

measure of a substance’s ability to transfer heat thru a solid by conduction

Answer 8

THERMAL CONDUCTIVITY

Question 9

The thermal conductivity of most liquids and solids varies with ______.

Answer 9

TEMPERATURE

Question 10

Thermal conductivity of vapors depends upon ______.

Answer 10

PRESSURE

Question 11

average temp. difference

Answer 11

LOG MEAN TEMPERATURE DIFFERENCE

Question 12

also called as a film coefficient

Answer 12

CONVECTIVE HEAT TRANSFER COEFFICIENT

Question 13

the thermal resistance of a relatively stagnant layer of fluid between a heat transfer surface and the fluid medium

Answer 13

CONVECTIVE HEAT TRANSFER COEFFICIENT

Question 14

combines the heat transfer coefficient of the two heat exchanger fluids and the thermal conductivity of the heat exchanger tubes

Answer 14

OVERALL HEAT TRANSFER COEFFICIENT

Question 15

For flow adjacent to a hot or cold surface, it is the temp. of a fluid that is far from the surface

Answer 15

BULK TEMPERATURE

Question 16

For boiling or condensation, Tb is equal to the _______.

Answer 16

SATURATION TEMPERATURE

Question 17

Heat transfer by conduction depends upon the driving force of ________ and the _______ to heat transfer.

Answer 17

TEMPERATURE DIFFERENCE, RESISTANCE

Question 18

It depends upon the nature and dimensions of the heat transfer medium.

Answer 18

RESISTANCE TO HEAT TRANSFER

Question 19

All heat transfer problems involve the temp. difference (ΔT), the ______, and the physical properties of the objects being studied.

Answer 19

GEOMETRY (AREA)

Question 20

Fourier’s Law of Conduction for Rectangular

Answer 20

Q = kA (ΔT/Δx)

Question 21

Fourier’s Law of Conduction for Cylindrical

Answer 21

Q = kA (ΔT/Δr)

Question 22

current flow is analogous to _______

Answer 22

HEAT TRANSFER RATE (Q)

Question 23

resistance is analogous to combination of _____, _____, and ______

Answer 23

THERMAL CONDUCTIVITY (k), THICKNESS (x), AREA (A)

Question 24

potential (emf) is analogous to ______

Answer 24

TEMPERATURE DIFFERENCE (ΔT)

Question 25

Fourier equation (Equivalent Resistance Method)

Answer 25

Q = ΔT/(Δx/kA) *analogous to I = V/R*

Question 26

Across a **cylindrical** wall, the heat transfer ______ is continually increasing or decreasing.

Answer 26

SURFACE AREA

Question 27

The evaluation of heat transfer thru a cylindrical wall can be extended to include a ________ composed of several concentric, cylindrical layers.

Answer 27

COMPOSITE BODY

Question 28

the motion and mixing is caused by **density** variations resulting from temp. differences within the fluid.

Answer 28

NATURAL CONVECTION

Question 29

the motion and mixing is caused by an **outside force (such as pump)**

Answer 29

FORCED CONVECTION

Question 30

T or F. Heat transfer by conduction is more difficult to analyze than heat transfer by convection.

Answer 30

FALSE (convection > conduction)

Question 31

T or F. Heat transfer by convection varies from situation to situation (upon fluid flow conditions), and is frequently with the mode of fluid flow.

Answer 31

TRUE

Question 32

In practice, analysis of heat transfer by convection is treated _______ or by direct observation.

Answer 32

EMPIRICALLY

Question 33

Factors that affect the stagnant film thickness

Answer 33

1. Fluid velocity 2. Fluid viscosity 3. Heat flux 4. Surface roughness 5. Type of flow (single/two-phase)

Question 34

T or F. Density of hot gas is higher than cold gas.

Answer 34

FALSE (cold > hot)

Question 35

For flow in pipe, Tb is the _______ measured at a particular cross-section of the pipe.

Answer 35

AVERAGE TEMPERATURE

Question 36

Convection heat transfer equation

Answer 36

Q = hAΔT

Question 37

______ is dependent upon the physical properties of the **fluid** and the physical situation.

Answer 37

CONVECTIVE HEAT TRANSFER COEFFICIENT (h)

Question 38

Typically, convective heat transfer coefficient for laminar flow is _______ than turbulent flow.

Answer 38

relatively low

Question 39

T or F. Laminar flow has a thinner stagnant fluid film layer on the heat transfer surface than turbulent flow.

Answer 39

FALSE (turbulent < laminar)

Question 40

Where applications involving convection heat transfer take place

Answer 40

within pipes, tubes, or some similar cylindrical device

Question 41

________ is used for heat transfer processes encountered in thermal facilities involving **both conduction and convection.**

Answer 41

OVERALL HEAT TRANSFER COEFFICIENT (Uo)

Question 42

The convective coefficient (h), the overall coefficient (Uo), and the other fluid properties may vary substantially for the fluid if it experiences a large ________ change during its path thru the convective heat transfer device.

Answer 42

TEMPERATURE

Question 43

Under such circumstances, the temperature at which the properties are **looked up** must be some type of _____ value rather than using either the inlet or outlet temperature value.

Answer 43

AVERAGE