Cooling Methods

Question 1

Commercial methods of cooling: (6)

Answer 1

Room
Force air
Hydrocooling
Package icing
Vacuum cooling
Transit cooling

Question 2

Describe room cooling:

Answer 2

produce in refrigerated room
cold air from ceiling -> cool produce
warmed air rises -> carries heat to cooling coils
repeat

Question 3

What is important for room cooling to be effective?

Answer 3

proper stacking/spacing (use pallets) - need some airflow

Question 4

advantages of room cooling: (4)

Answer 4

less handling
simple
moderate refrigeration load
moderate air flow

Question 5

disadvantages of room cooling:

Answer 5

slow

Question 6

If air flow is too fast, _____

If air flow is too slow, ______

Answer 6

fast -> dessication

slow -> longer cooling

Question 7

What should air flow be in a cooling room, vs a storage room?

Answer 7

cooling: 200-400fpm
storage: 50-75fpm

Question 8

True/False: There should be plenty of empty space in a cooling room

Answer 8

false; should minimize

but ensure good ventilation

Question 9

What are examples of modified room cooling?

Answer 9

Ceiling jets (air from jets direct to produce - better circulation) 
Cooling bays (individually controlled rooms)

Question 10

Forced air cooling is also known as _____. It is based on:

Answer 10

suction/pressure cooling

force high velocity cool air flow, using NEGATIVE PRESSURE

Question 11

How does air flow differ in room vs forced air cooling?

Answer 11

room: air flow AROUND packages

forced air: air flow THROUGH packages (need ventilation slits)

Question 12

What is an essential component of forced air cooling systems?

Answer 12

fans/blowers to pull air away, creating negative pressure and drawing more cool air through

Question 13

“cold-wall” and “serpentine” coolers are examples of modified ____ cooling

Answer 13

forced air

Question 14

increasing ventilation in a package will have the negative effect of:

Answer 14

decreasing strength

Question 15

What is hydrocooling and what are the advantages? (3)

Answer 15

use water as cooling medium

better heat transfer than air (h)
no moisture loss
cleansing

Question 16

Hydrocooling can be a ___ or ____ process, and can be a ____ or ___ system

Answer 16

continuous/batch

spray/immersion

Question 17

Important considerations/limitations of hydrocooling: (4)

Answer 17

not good for packaged goods (unless water tolerant)
need clean water
produce should be Cl resistant (from water)
must transfer to cold storage quick

Question 18

Important considerations for package icing:

Answer 18

water resistant package
drainage holes
cold environment

Question 19

advantages of package icing:

Answer 19

fast cooling (vaporization + contact cooling)
tight packing OK
High RH -> less moisture loss

Question 20

When was vacuum cooling developed?

Answer 20

1940s

Question 21

How does vacuum cooling work?

Answer 21

vacuum lowers partial pressure of air (Pwa)

MUCH HIGHER WVPD -> bigger driving force for evaporation!

RAPID EVAP. of water (flashing) -> cooling + moisture loss

Question 22

What happens to wet bulb temperature and wet bulb depression as the vacuum increases?

Answer 22

wet bulb: decrease

wet bulb depression: increase

Question 23

As the vacuum increases, the boil pt. of water will ____. This results in:

Answer 23

decrease

flashing (rapid evaporation)

Question 24

What are the basic components of a vacuum cooling system?

Answer 24

strong vacuum chamber (leak proof)
vacuum device (mechanical/steam injection)
condenser (water/coils)

Question 25

What can be done to make vacuum cooling even more effective?

Answer 25

wetting of produce

Question 26

Factors affecting vacuum cooling: (4)

Answer 26

surface area
porosity
degree of vacuum
water availability

Question 27

Vacuum cooling systems are best suited for: _____, and are (low/high) cost.

Answer 27

produce with large SA:volume ratio

high