cooling and cold chain technologies in general.

Cooling and cold chain systems are essential for maintaining the quality and safety of temperature-sensitive products, such as food and pharmaceuticals, throughout storage and transportation. A cold chain ensures that products remain within specific temperature ranges from production to consumption, preventing spoilage and degradation. This involves refrigeration units for storage, refrigerated transport methods, and real-time monitoring systems to detect any temperature fluctuations. Proper cold chain management reduces waste, extends shelf life, and ensures the integrity of products, especially in industries like healthcare and food distribution.

1. ADD YOUR TITLE HERE
AGM301 COOLING AND COLD CHAIN Part 1
by:
Quenan Gasana
E-mail: [email protected]

2. 0Why this topic?

3. 0
▪Foodscanbecomespoiledduetochemicalreaction,physicalreactionor
actionof microbes.
▪Microbesarepresentin air,water,soilandalsoin thefoodweconsume.
▪Loweringthetemperatureslowsdowntherapidrateofthesebacterial
growthin foods.Mostbacteriagrowatatemperatureof4°C(40°F)to60°C
(140°F). Thisisthebasicprinciplebehindprolongingshelflifeofthefoods
weconsume throughrefrigeratedstorage.
Why this topic?

4. 0What is Cooling and Cold Chain?

5. 0
1.Define and explain the basic postharvest
handling and treatment for smallholder
farmers, achieved
5.Analyze and evaluate the feasibility of
establishing and operating Agro-processing
industries,
2.Analyze challenges and solutions in Cooling
and cold chain management in developing
countries,
6.Produce a product/Service to reduce
postharvest-losses for smallholder
farmers in Rwanda.
3.Innovate and implement mechanical
solutions to effectively minimize
postharvest losses,
4.Apply advanced technologies and techniques to
enhance the value addition to agricultural produce,
Learning outcome
Upon successful completion of this course, students will be able to:

6. 0Content
Pre-cooling of horticultural crops
Refrigerant
Important terminologies and refrigeration system
Refrigeration system accessories
Cold storage design

7. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling-Purpose
▪Removal of field heat
▪Reduce energy required for cold storage
▪Marketing flexibility
✓Market at an optimum time (economy & quality)
✓Market over a longer distance

8. 1PRE-COOLING OF HORTICULTURAL CROPS
Importance of pre-cooling
▪Pre-cooling is the first step of good
temperature management of fruits and
vegetables after harvest.
▪It is essential practice in any successful cool
chain management of horticultural produce.
▪However, time and temperature are the two
most important features of pre-cooling.
▪Speed of cooling depends upon:
✓Accessibility of produce to the refrigerating
medium,
✓Difference between the temperature of
produce and refrigerating medium,
✓Velocity of refrigerating medium
Pre-cooled-
Alive& Happy
Not-Precooled-
Faster Sick and Die
Effectofpre-cooling

9. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling temperature
▪Generally, horticultural produce are cooled to
their storage temperature i.e.,
✓For example, grapes are cooled to 1-4°C,
potato to 5–9°C,
✓Mango, tomato & banana to be cooled to >
10 °C.
▪All fruits and vegetables are mostly cooled by
room cooling and or mechanical refrigeration.

10. 1PRE-COOLING OF HORTICULTURAL CROPS
Advantages of Pre-cooling
Benefit of pre-cooling
▪Prevent wilting
▪Slow the decay rate
▪Prevent quality loss due to softening
▪Reduce ethylene production
▪Minimize the impact of ethylene
Inhibition of the growth of decay causing organisms,
Restriction of the enzyme activities,
Reduction of water loss from the harvested produce, Reduction
in rate of respiration and ethylene (C2H4)
liberation, and
Rapid wound healing.

11. 1PRE-COOLING OF HORTICULTURAL CROPS
Principles of cooling
Selecting pre-cooling technique
▪Cooling temperature 0 – 14°C
▪Reduce temperatures via different means
Directcooling
Heatsinkmedium
e.g.coldwater,
iceandmixture
Heatout
Indirectcooling
Heatsinkmedium
e.g.coldair,cold
metal
Heatout
▪Nature of the produce
✓Temperature requirement
✓Susceptibility to wetting
▪Package design
▪Production capacity
▪Economic factors
▪Social factors

12. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
Room cooling
▪Air cooling
✓Room cooling
✓Forced air cooling
▪Hydro cooling
▪Ice cooling
✓Top icing
✓Liquid icing
✓Individual package icing
▪Vacuum cooling
▪Evaporative cooling
▪Insulated room equipped with refrigeration unit
▪Disadvantage
✓Slow cooling rate
✓Not suitable for produce in large
containers
1. Air Cooling

13. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
Forced-air cooling
▪Fan assisted room-cooling
▪The fan pulls cool air through packaged produce and forces
the hot air to leave the package
▪Cooling rate depends on temperature and the air flow rate
▪75 – 90% more efficient than room cooling
Anona Coconut Mango Pumpkin
Avocado Cucumber Melons Rhubarb
Banana Eggplant Okra Strawberry
Breadfruit Grape Orange SummerSquash
BrusselssproutGrapefruit Papaya Tangerine
Carambola Guava Passionfruit Tomato
Cassava Kiwi Pepper Pineapple
Cherimoya Kumquat Persimmon
Pomegranate Litchi Pricklypear
1. Air Cooling

14. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
2. Hydro-cooling
▪The flow of chilled water over produce
▪Disadvantages
✓Limited to produce that are not sensitive to wetting
✓Not energy efficient (20-40% efficiency)
▪Critical point
✓Good water sanitization practice
✓Proper packaging
Hydro-cooling-Packaging
▪Wire-bound wooden crates
▪Waxed fiberboard cartons
✓Should not have solid top
▪Mesh bags
▪Bulk bin
Hydro-cooling Produce

15. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
3. Ice-cooling
▪Ice continues to absorb heat as it melts
▪Suitable for
✓Produce with high respiration rate
✓Dense product or palletized packages
▪Relatively energy efficient
✓1 lb of ice cool 3 pounds of produce (85°F to 40°F)
▪Maintain low temperature during transportation
Liquid icing
▪Crushed ice is added over the top of the produce
Broccoli, Carrot, Leek
Brussels sprouts, Chinese cabbage, Parsley
Cantaloupe, Green onions, Peas
Top-icing
Individual package icing
▪Add measured amount of crushed ice
over the produce
▪Disadvantages
✓Uneven cooling
✓Labor intensive
✓Limited to low volume product
▪Some automated system is available
using ice dispenser & conveyor
▪Injecting slurry of ice & water into the package
through vents or hand holes
▪Excellent cooling method for both large & small
operation
▪Disadvantages
✓Limited to produce that are not sensitive to wetting
✓Warm, wet produce is prone to post harvest
diseases

16. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
3. Ice-cooling Ice-cooling: packaging
▪Hold strength after wetting
▪Example
✓Wax fiberboard cartons:
oMinimal openings
oInsulation properties
✓Baskets
✓Wooden wire-bound crates
✓Hampers
✓Perforated plastic liners
Producecan beicedProducecanbedamagedby
directcontactwithice
Artichokes Strawberries
Asparagus Blueberries
Broccoli Raspberries
Leafygreen Tomatoes
Watermelon,
cantaloupe
Greenbeans
Carrot Cucumbers
Radishes Herbs
Spinach Garlic
Sweetcorn
Squash

17. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
4. Vacuum cooling
▪Vacuum around the produce causes water to
evaporate rapidly thus reducing the temperature
▪Vacuum is created by putting produce in the metal
container. Then, the air is evacuated
▪Disadvantage: wilting (if overdone)
▪Hydro vacuum cooling
oSpray water onto the produce before vacuum
process
Produce
▪High surface: volume ratio
▪Produce difficult to cool with Forced-
air or Hydro-cooling
BrusselssproutsChinesecabbage Snapbeans
Carrot Leek Spinach
Cauliflower Lettuce Sweetcorn
Celery Peas Swiss
chard

18. 1PRE-COOLING OF HORTICULTURAL CROPS
Pre-cooling techniques
5. Evaporative cooling
▪Misting/wetting in the presence of
dry air stream (RH<65%) to cause
evaporation
▪Effective and inexpensive means of
providing low temperature & high
RH conditions
▪Good for warm season crop such as
tomatoes, pepper, cucumbers or
eggplant
Comparison of cooling method

19. 1PRE-COOLING OF HORTICULTURAL CROPS
ALTERNATIVE COOLING METHODS
Solar assisted cooling chamber
▪Temporary fruit storage at farm
▪Hollow wall constructed from
porous clay bricks
▪The wall is kept moist
▪Solar energy evaporated the water
in the wall reduce temperature
▪Can achieve
o4-5°C < ambient
o85-90% RH inside the structure
High altitude storage
▪Every 1000 m, the temperature
decreases by 1.8°F (1°C)
▪Storing produce at high altitude
reduce energy required for cooling
Night ventilation
▪Requires
oLarge temperature difference
between day and night
oWell insulated structure
oClose vents hole early in the
morning

20. 2Refrigerant
Refrigerant
▪Workingfluidintherefrigeration
▪Itiscapableofabsorbingheatatlowertemperatureandrejecting heat at
highertemperatureintheformofsensibleheatandlatentheat.
Ice
Water Vapour
LatentHeatofMelting
LatentHeatofFreezing
LatentHeatofVaporization
LatentHeatofCondensation
SensibleHeat SensibleHeat SensibleHeat

21. 2
SensibleHeat(thatcanbesensed/felt)
▪Itistheenergymovingfromonesystemto
anotherthatchanges thetemperature
without changingitsphase.
▪Whenthesubstanceisheated,andthe
temperature rises, so the heat added is
called sensibleheat.
▪This increase in heat can be felt physically
or measuredwithordinarythermometer.
LatentHeat
▪The heat needed to change one form of
matter to another without change in
temperature. So, it can be latent heat of
vaporization or latent heat of condensation.
Refrigerant

22. 2
CharacteristicsofRefrigerant
•shouldbehighLatentheatofvaporization
•shouldbelowCondensingpressure
•should belowFreezingtemperature
•shouldbehighCriticaltemperature
•should be nontoxic, nonflammable,non-corrosive and
chemicallystable
Toxicity,flammability,corrosionand
chemicalstability
•should belowCost
•anyleakofrefrigeranttotheenvironmentshouldnotcause
anyharm
Environmentfriendly
Refrigerant

23. 2
Classification Refrigerants
Refrigerants
Primary
Refrigerants
Used directly as
working fluids.
Undergo phase
change. eg.,
R134a, R404a
Secondary
Refrigerants
Liquids that are
used to transport
energy.
Not undergo and
phase change eg.,
Water , brines.
Primary refrigerants
▪Cool the substance or space directly by
absorbing latent heat.
▪It absorbs heat during evaporation in the
evaporator and releases heat energy during
condensation in condenser.
▪E.g. Ammonia, Freon, SO2, CO2 etc.
▪These fluids provide refrigeration by
undergoing a phase change process in the
evaporator.
Secondary Refrigerants
▪In refrigeration plant a secondary coolant is
used as cooling medium which absorb heat
from refrigerated space and transfer to
primary refrigerant in evaporator.
Secondary refrigerants are also known
under the name brines or antifreezes
Refrigerant

24. 2
Classification Of Primary Refrigerant
Examples :
oCFC’s : R11, R12, R113, R114, R115
oHCFC’s : R22, R123
oHFC’s : R134a, R404a, R407C, R410a
1. Halocarbon
Refrigerants
Are all synthetically produced and were developed as the Freon family of refrigerants.
They contain 1 or more of these halogens (chlorine, bromine, fluorine)
Composition:
Chlorofluorocarbons (CFCs), Hydrochlorofluorocarbons (HCFCs), Hydrofluorocarbons
(HFCs)
Types:
Nontoxic, non-flammable, non-explosive, non- corrosive, non-irritant to human body and
eyes, Odorless, colorless, Will not react with food product stored in the refrigerated
space, Will not react with lubricating oil.
Properties:
Refrigerators and freezers, Air conditioning systems, Heat pumps, Industrial cooling
processes
Applications:
CFCs and HCFCs deplete the ozone layer, Many halocarbon refrigerants are potent
greenhouse gases
Environmental
concerns:
Refrigerant

25. 2
Freon Group Refrigerants Application and ODP
Values
Refrigerant Areas of Application ODP
CFC 11(R11)
CFC 12 ( R 12 )
CFC 13 (R 13)
CFC113 ( R113 )
CFC114 ( R114 )
Blend of R22 and
R115 (R502)
▪Air-conditioning Systems ranging from 200 to 2000 tons in capacity.
It is used where low freezing point and non-corrosive properties are
important.
▪It is used for most of the applications. Air-conditioning plants,
refrigerators, freezers, ice-cream cabinets, water coolers, window
air-conditioners, automobile air conditioners.
▪For low temp refrigeration up to – 90 C in cascade system
▪Small to medium air-conditioning system and industrial cooling
▪In household refrigerators and in large industrial cooling
▪Frozen food ice-cream display cases and warehouses and food
freezing plants. An excellent general low temp refrigerant
1.0
1.0
1.0
1.07
0.8
0.34
Refrigerant

26. 2
2. Inorganic Refrigerants
▪Inorganic refrigerant were exclusively used before the introduction
of halocarbon.
▪These refrigerant are still in use due to there inherent
thermodynamic and physical properties.
•Carbon Dioxide
•Water
•Ammonia
•Air
•Sulphur dioxide
Refrigerant

27. 2
2. Inorganic Refrigerants
▪Used for commercial purposes mainly in cold stored and ice plants.
▪The boiling temperature of NH3 at atmospheric pressure is -33 ºc and melting
point from solid is -78ºC The low boiling points makes it possible to have
refrigeration considerably below 0ºC without using pressure below atmospheric
in the evaporator.
▪Its latent heat of vaporization at -15ºC is 1315 k/kg
▪It is colorless gas with a sharp pungent smell
▪Has good thermodynamic properties
▪It is neutral to all metals, highly soluble in oil.
▪Volatile and non-toxic but in higher conc.
Ammonia (NH3) R-717
Refrigerant

28. 2
2. Inorganic Refrigerants
▪Previously used in household refrigerators
▪Toxic, non-explosive and non-flammable, non-corrosive
▪Irritant to human body
▪Non mixable with oil
▪Has pungent odor and low latent heat value
Sulphur Dioxide (So2)
Refrigerant

29. 2
3. Azeotrope Refrigerants
▪This group of refrigerants consist of mixture of different refrigerants which can not
separated under pressure and temperature and have fixed thermodynamic
properties.
▪A stable mixture of two or several refrigerants whose vapor and liquid phases
retain identical compositions over a wide range of temperatures.
▪Azeotropic mixtures are designated by 500 series
▪Examples :
•R-500 :( 73.8% R12 and 26.2% R152)
•R-502 : (8.8% R22 and 51.2% R115)
•R-503 : (40.1% R23 and 59.9% R13)
Refrigerant

30. 2
4. Zeotropic Refrigerants
▪A zeotropic mixture is one whose composition in liquid phase differs to that in
vapor phase. Zeotropic refrigerants therefore do not boil at constant temperatures
unlike azeotropic refrigerants.
▪zeotropic refrigerants (e.g. non-azeotropic mixtures) are designated by 400 series.
▪Examples :
•R404a : R125 /R143a /R134a (44%,52%,4%)
•R407c : R32/R125/R134a (23%, 25%, 52%)
•R410a : R32/R125 (50%, 50%)
•R413a : R600a/ R218/R134a (3%, 9%, 88%)
Refrigerant

31. 2
5. Hydrocarbons
▪Most of the hydrocarbon refrigerant are successfully used in industrial and
commercial installation . They possess satisfactory thermodynamic properties
but are highly flammable and explosive.
▪Growing use in very small commercial systems like car air-conditioning system
▪Examples:
•R170, Ethane, C2H6
•R290 , Propane C3H3
•R600, Butane, C4H10
•R600a, Isobutane, C4H10
•Blends of the above Gases
Refrigerant

32. 2
Secondary Refrigerant
▪The refrigerants are brine which is used as intermediate fluid between evaporator and the substance or space to
be cooled. They cool the substance and the space by absorbing their sensible heat. Also called indirect
expansion system.
•Eg. Brine solution made of calcium chloride or sodium chloride
▪Water cannot be used as secondary refrigerant because at 0 ºC itself it will become ice and circulation is not
possible. In brine solution CaCl2 is much preferred, it is very costly
▪Choice of brine depends on temperature to which a material is to be cooled and industrial process in which it is
to be used. The calcium chloride brine has eutectic temperature of -55 ℃ at salt concentration of 30% by mass.
The sodium chloride brine has eutectic temperature of -21.1 ℃ at salt concentration of 23% by mass
▪Freezing point of brine depends on its concentration. Cheapest secondary refrigerants are water and air but their
application is limited. Since, water has a high freezing point (00C) and air has a low heat capacity.
Refrigerant

33. 2
Designation of refrigerants:
▪Since a large number of refrigerants have been developed over the years for a wide variety
of applications, a numbering system has been adopted to designate various refrigerants.
From the number one can get some useful information about the type of refrigerant, its
chemical composition, molecular weight etc. All the refrigerants are designated by R
followed by a unique number.
Environmental and safety properties
▪Ozone Depletion Potential (ODP)
▪Global Warming Potential (GWP):
▪Total Equivalent Warming Index (TEWI)
▪ Toxicity
▪Flammability
▪Chemical stability
▪Compatibility with common materials of construction
▪Miscibility with lubricating oils:
Refrigerant

34. 2
Boiling Temperature
Refrigerant Boiling Temperature
at atm pressure
R-11 +21.77
R-12 -29
R-21 +9
R-22 -41
R-30 +39.8
R-40 -23.7
R-113 +47.6
R-717 -33.3
R-764 -10
Refrigerant
Freezing Temperature
Refrigerant Freezing
Temperature
R-11 -111
R-12 -157.5
R-21 -135
R-22 -160
R-30 -96.9
R-40 -97.5
R-113 -35
R-717 -77.8
R-764 -75.6

35. 3Important terminologies and refrigeration system
1. Coolingload
▪Coolingloadistherateofremovalofheatfromadefinedspacein
order tolowerthetemperatureofthatspacetoadesiredlevel.
▪The cooling loads of refrigeration systems are designated with a
commonunitcalledtonofrefrigeration(TR).
2. Tonofrefrigeration(TR)
▪Amountofheatrequiredtoberemovedfromonetonofwaterat0°Cin
ordertoconvertitintoiceat0°Cinoneday(24hours).
▪1TR= 12600 KJ/h or 210 KJ/min or 3.5 KW

36. 3
3. CoefficientofPerformance(COP)
▪The efficiency of the refrigeration system is also indicated as
CoefficientofPerformanceofthesystem.
▪Itistheratiooftheheatextractedintherefrigeratortothework
doneon therefrigerant.
▪COP =Amount of heat extracted in the refrigerator (Q)
Amountofworkdone(W)
COP=Q
W
Important terminologies and refrigeration system

37. 3
4. RelativeHumidity
▪Itistheactualmassofwatervapourinagiven
volumeofmoistairtothemassofwatervapourin
thesamevolumeofsaturatedairatthesame
temperature.
Important terminologies and refrigeration system

38. 3
Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1
2
3
4
▪Refrigeration systemisbasedonthe
principlethatabsorptionofheatbya
fluid (refrigerant)asitchangesfroma
liquidtoagas,lowersthe temperature
oftheobjectsaroundit.
▪The most common type of refrigeration
system applying this principle is Vapour
Compression Refrigeration (VCR)
System.
▪The VCR System is widely used in
refrigeration applications like
refrigerator, water cooler, air
conditionerand cold storage.
▪Therefrigerationeffectisproducedat
the evaporator.
Important terminologies and refrigeration system

39. 3
Low Pressure Low
Temperature
Vapour
High Pressure High
Temperature Vapour
High Pressure High
Temperature Liquid
Low Pressure Low
Temperature Liquid
Compressor
Condenser
Expansion
Valve
Evaporator
RefrigerationSystem
Heat
Important terminologies and refrigeration system

40. 3Important terminologies and refrigeration system

41. 3
▪The low-pressure low temperature liquid
refrigerant absorbs and removes heat from the
inside cabinet.
▪This low-pressure refrigerant from evaporator turns
into saturated vapor which is then compressed
water- or air-cooled high
▪pressure and passed to the condenser. The heat is
rejected in the condenser. Then the saturated liquid
refrigerant enters the expansion valve, where it is
undergoes pressure reduction.
▪After expansion valve the refrigerant again enters
the evaporator and the cycle continues. A fan is
used to force the warm air over the evaporator
coils. The condenser may be water or air-cooled
type.
Important terminologies and refrigeration system