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WorksheetsM6 HeMaTra
Total questions: 21
Worksheet time: 16mins
HEAT EXCHANGERS:
TUBULAR STRUCTURE
double-pipe
shell-and-tube
plate-fin
plate-and-frame
HEAT EXCHANGERS:
STACKED STRUCTURE
double-pipe
shell-and-tube
plate-fin
plate-and-frame
Economic considerations are important in engineering design, and in a complete engineering design of heat exchange equipment not only the (1) characteristics but also the (2) requirement and the (3) of the system are important.
thermal performance
pumping power
economics
all of the above
In heat exchanger design, the following should be considered: economics, availability and amount of energy, and raw materials necessary.
TRUE
FALSE
BASIC TYPE OF HEAT EXCHANGERS:
RECUPERATORS.
SELECT WHICH IS/ARE INCORRECT.
separated by a wall
hot and cold fluids alternately occupy the same space
wall can include extended surfaces
heat is transferred by a combination of convection and conduction
REGENERATORS.
SELECT WHICH IS/ARE CORRECT.
hot and cold fluids alternately occupy the same space in the matrix
In a fixed matrix configuration, the hot and cold fluids pass alternately through a stationary exchanger
for continuous operation two or more matrices
are necessary
none of the above
Double–pipe heat exchanger.
The following statements are TRUE:
the simplest heat exchanger
concentric pipe exchanger
useful mainly for larger flow rates
the most important in the process industries
shell-and-tube heat exchanger.
The following statements are TRUE:
flows are continuous
made from a number of pairs interconnected in series
made from a pair of single lengths of pipe with fittings at the ends
Many tubes in parallel are used
In this type of heat exchanger, the hot and cold fluids contact each other directly.
Direct Contact Heat Exchangers
Regenerators
Recuperators
Double–pipe heat exchanger
(select all that apply)
PARALLEL FLOW
COCURRENT FLOW
COUNTER FLOW
SHIKU FLOW
(select all that apply)
PARALLEL FLOW
COCURRENT FLOW
COUNTER FLOW
SHIKU FLOW
For the computation for LMTD, the changes in
temperature (Δ𝑇1 and Δ𝑇2) are not pertaining to the differences in the initial and final temperatures. Instead, they are termed as (1) , the difference of the temperatures of the two fluids at the (2) points. Thus, counter flow LMTD is (3) from parallel flow LMTD.
(SEPARATE ANSWERS BY ",")
(a)
During operation with most liquids and some gases, a deposit gradually builds up on the heat transfer surface. The deposit may be
rust
boiler scale
silt
coke
select which is/are true for fouling
increases thermal resistance
nature of the dirt deposit or the rate of fouling can be predicted
thermal resistance of the deposit can generally be obtained only from actual tests or from experience
all of the above
SHELL AND TUBE HEAT EXCHANGERS
The fluid is forced to flow over the tubes rather than along the tubes because a higher heat transfer coefficient can be achieved in cross–flow than in flow parallel to the tubes.
TRUE
FALSE
These (1) ensure that the flow passes across the tubes in each section, flowing downward in the first, upward in the second, and so on. The most
common kind is the (2).
(SEPARATE ANSWERS BY ",")
(a)
PARALLEL FLOW.
Select which is/are true
a & b
a. the higher the APPROACH the better the HEAT TRANSFER RATE
b. more common in the industry
none of the above
Several factors must be considered in deciding which fluid to put in the tubes and which to put in the shell of a shell and tube heat exchanger.
SELECT WHICH IS/ARE TRUE.
If one of the fluids is quite corrosive it should be put in the tubes
one of the fluids is dirty and likely to form deposits on the wall, it should be put in the shell side
Very hot fluids it should be put in the tubes
Very viscous fluids it should be put in the in the shell side
The heat exchanger effectiveness is defined as the ratio of the actual rate of heat transfer in a given heat exchanger to the maximum possible rate of heat exchanger.
The latter would be obtained in a (1) flow heat exchanger of (2) heat transfer area
(1) counter
(1) parallel
(2) infinite
(2) finite
The number of heat transfer units is a measure of the heat transfer size of the exchanger. The (1) the value of NTU, the (2) the heat exchanger approaches its thermodynamic limit.
larger, closer
smaller , closer
larger, farther
smaller, farther
(1) are devices or systems in which heat is transferred from flowing fluid to another. These devices may have a (2) structure or a (3) structure.
(SEPARATE ANSWERS BY ",")
(a)
