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Process Design and Safety > Pinch Design Method > Flashcards

Pinch Design Method Flashcards

1
Q

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

A

Process to process heat transfer

Inappropriate use of utilities

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2
Q

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

A

Steam; cooling water

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3
Q

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

A

Pinch

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4
Q

CPh <= CPc ______ the pinch

A

Above

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5
Q

CPh >= CPc _____ the pinch

A

Below

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6
Q

______ utility must not be used above the pinch.

A

Cold

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7
Q

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

A

Above

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8
Q

Match hot streams to cold streams_______ the pinch

A

Above

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9
Q

Hot utility must not be used _____ the pitch

A

Below

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10
Q

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

A

Below

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11
Q

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

A

Capital cost

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12
Q

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

A

Tick-off heuristic

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13
Q

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.

A

Hot streams

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14
Q

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.

A

Pinch; splitting; parallel

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15
Q

Sh <= Sc _____ the pinch

A

Above

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16
Q

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.

A

Above; hot utility

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17
Q

Sh >= Sc _____ the pinch

A

Below

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18
Q

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

A

Flow rates

19
Q

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

20
Q

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

A

Low pressure

21
Q

Below the process pinch only _____ ____ should be used

A

Cooling water

22
Q

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

A

Equalities

23
Q

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

24
Q

What is the heat exchange between to process streams called?

25
Q

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

A

Heater or cooler

26
Q

When a process stream is completely vaporized it is called a

27
Q

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

28
Q

What is used to concentrate a solution

A

Evaporator

29
Q

What do you use when heating is done by combustion?

A

Fired heater

30
Q

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

A
  • duty
  • stream conditions
  • configuration
31
Q

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

A

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

32
Q

What is the equation for heat transport?

A

Q=UAdeltaT

33
Q

What is the equation for overall resistance?

34
Q

What is the most commonly used heat exchanger?

A

Shell and tube

35
Q

What are advantages of shell and tube exchangers?

A

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

36
Q

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

A

Q=mass flowrate * heat capacity * delta T

37
Q

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

A

Q= mass flowrate times lamda

38
Q

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

39
Q

Lines should not approach each other too closely. Why?

A

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

40
Q

What is the closest approach called?

A

Pinch point

41
Q

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

A

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

42
Q

What are important assumptions made by the heat flow equation?

A

U is constant

No heat is lost to ambient environment

43
Q

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

A

Split hot stream

44
Q

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

A

Split the cold stream

Process Design and Safety (6 decks)

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