Pinch Design Method

Question 1

The design must not transfer heat across the pinch by what 2 rule?

Answer 1

Process to process heat transfer

Inappropriate use of utilities

Question 2

Above the pinch ______ can be used up to QHmin and below the pinch _______ ______ can be used up to QCmin.

Answer 2

Steam; cooling water

Question 3

The ______ is the most constrained region of the problem and is what your design should start with.

Answer 3

Pinch

Question 4

CPh <= CPc ______ the pinch

Answer 4

Above

Question 5

CPh >= CPc _____ the pinch

Answer 5

Below

Question 6

______ utility must not be used above the pinch.

Answer 6

Cold

Question 7

Hot streams can be used on the cold streams ______ the pinch.

Answer 7

Above

Question 8

Match hot streams to cold streams_______ the pinch

Answer 8

Above

Question 9

Hot utility must not be used _____ the pitch

Answer 9

Below

Question 10

It is essential to match cold streams _______ the pinch with a hot stream

Answer 10

Below

Question 11

The number of units is an important criterion in the ______ _____

Answer 11

Capital cost

Question 12

Keeping the number of units to a minimum can be achieved using the ____-______ _________.

Answer 12

Tick-off heuristic

Question 13

Cooling water must not be used above the pinch, therefore, if there are ____ _____ above the pinch for which the pinch matches do not satisfy duties, additional process to process heat recovery is required.

Answer 13

Hot streams

Question 14

If there are 3 hot streams and 2 cold streams, one of the hot streams cannot be cooled to the ______ temperature. The problem can be resolved by _______ a cold stream into two _______ branches.

Answer 14

Pinch; splitting; parallel

Question 15

Sh <= Sc _____ the pinch

Answer 15

Above

Question 16

If there had been a greater number of cold streams than hot streams in the design _____ the pinch, this would not have created a problem since _____ _____ can be used above the pinch.

Answer 16

Above; hot utility

Question 17

Sh >= Sc _____ the pinch

Answer 17

Below

Question 18

There is a degree of freedom in the design to choose the branch _____.

Answer 18

Flow rates

Question 19

______ the utility pinch; high-pressure steam should be used and no low-pressure steam or cooling water.

Answer 19

Above

Question 20

Between the utility pinch and process pinch _____ _____ steam should be used and no high - pressure steam or cooling water

Answer 20

Low pressure

Question 21

Below the process pinch only _____ ____ should be used

Answer 21

Cooling water

Question 22

Away from the pinch there is more flexibility and the ______ do not have to hold

Answer 22

Equalities

Question 23

When trying splitting above the pinch start with cold streams with highest ________

Answer 23

Cp

Question 24

What is the heat exchange between to process streams called?

Answer 24

Exchanger

Question 25

A process stream is heated or cooled by a utility stream called a what?

Answer 25

Heater or cooler

Question 26

When a process stream is completely vaporized it is called a

Answer 26

Vaporizer

Question 27

A vaporizer that is associated with a distillation column is called a what?

Answer 27

Rebuilder

Question 28

What is used to concentrate a solution

Answer 28

Evaporator

Question 29

What do you use when heating is done by combustion?

Answer 29

Fired heater

Question 30

What do we need when we want to design heat transfer equipment?

Answer 30

* duty * stream conditions * configuration

Question 31

What do we need to solve heat transfer equipment design problems?

Answer 31

Physical properties, U (both h and k), Heat transport, overall resistance

Question 32

What is the equation for heat transport?

Answer 32

Q=UAdeltaT

Question 33

What is the equation for overall resistance?

Answer 33

R=1/(UA)

Question 34

What is the most commonly used heat exchanger?

Answer 34

Shell and tube

Question 35

What are advantages of shell and tube exchangers?

Answer 35

Large surface area in small volume Good mechanical layout Well established fabrication methods Can be constructed from a wide variety of materials Easily cleaned and maintained Well established design procedures

Question 36

What is the equation for heat transport for single phase streams with constant cp and no pressure effect on enthalpy?

Answer 36

Q=mass flowrate * heat capacity * delta T

Question 37

What is the equation for heat flow when pure components are undergoing a phase change?

Answer 37

Q= mass flowrate times lamda

Question 38

T-lines for counter-current flows do not what?

Answer 38

Cross

Question 39

Lines should not approach each other too closely. Why?

Answer 39

As they approach, the area required for heat transfer goes to infinity

Question 40

What is the closest approach called?

Answer 40

Pinch point

Question 41

What is the heat transfer rate equation for single pass heat exchangers?

Answer 41

Q = UA((delta T2 - delta T1)/ln(delta T2/delta T1))

Question 42

What are important assumptions made by the heat flow equation?

Answer 42

U is constant | No heat is lost to ambient environment

Question 43

If FCph is greater than FCpc above the pinch point what should you do?

Answer 43

Split hot stream

Question 44

Below the pinch point, if FCpc > FCph what should you do?

Answer 44

Split the cold stream