Refrigeration in Agriculture

Electricity for Cooling

• Presented by Engr. Alexis T. Belonio, Department of Agricultural Engineering and Environmental Management, College of Agriculture, Central Philippine University, Iloilo City.
• Contact: [email protected]

Application of Refrigeration and Cold Storage of Crops

• Preserves and stores farm produce like eggs, milk, meat, vegetables, fruits, and flowers.
• Extends the storage time of grain seeds.
• Maintains the freshness of newly caught fish before processing.

Refrigeration Equipment

• Various types of refrigerators and chillers are shown.

Farm Structures and Offices

• Properly ventilating farm structures (like poultry houses, dairy farms, crop conditioning facilities) improves the environment inside.
• Better ventilation leads to improved conditions in farm houses and offices.

Principles of Refrigeration

• Refrigeration works by removing heat to lower the temperature of a substance or space.
• Refrigeration systems take heat from an enclosed space and release it outside.

Refrigerant

• A refrigerant is a substance that absorbs heat from a refrigerated space and releases it outside.
• Common refrigerants include:
  • Ammonia (oldest and widely used for large installations)
  • Methyl chloride
  • Sulfur dioxide
  • Freons (commonly used today).

Properties of Refrigerants

• Properties of various refrigerants are listed in a table, including refrigerating effect (BTU/lb) per standard cycle and remarks.

Evaporation

• Evaporation changes liquid refrigerant to gas.
• Adding heat to the refrigerant causes evaporation.
• Evaporation of refrigerant lowers the temperature of the surrounding area.
• The evaporator is located inside the refrigerated space to absorb heat.

Condensation

• Condensation transforms gaseous refrigerant back into liquid.
• Heat must be removed from the refrigerant to condense it.
• The cooler space removes heat from the refrigerant, causing condensation.
• Condensers are positioned outside refrigerated spaces to release the absorbed heat.

Refrigeration Cycle

• The complete series of events as the refrigerant flows through the system.
• Includes specific parts like condenser, compressor, expansion valve, and evaporator.

Refrigeration Cycle Details

• The refrigeration cycle consists of four key steps:
  • Expansion: High-pressure liquid refrigerant flows through a valve to a low-pressure pipe, expanding and lowering its temperature.
  • Evaporation: The now lower-temperature liquid refrigerant absorbs heat from the refrigerated space, changing to a gas.
  • Compression: The gaseous refrigerant is compressed by a compressor, increasing its temperature and pressure.
  • Condensation: The hot, high-pressure gaseous refrigerant releases heat to the outside environment, changing back into a liquid.

Electrical Control for Refrigeration

• Various components control a refrigeration system.
• Components include:
  • Manual disconnect switch for maintenance/safety
  • Time delay fuses for additional protection
  • Thermostat to control operation.
  • Solenoid valve for refrigerant flow control.
  • Pressure switch (low/high pressure).

Quantities in Refrigeration

• Heat required to cool the product, lowering temperature.
• Heat removed to cool the refrigerated space, focusing on heat transfer from outside elements.

Heat Removed from the Product

• Calculating heat removal for cooling products.

  - Formula: Q product = specific heat x mass of product x temperature difference

• Example: Calculating BTU required to cool 200 lbs of fresh beef from 90F to 40F.

Specific Heat of Farm Products

• Table showing the specific heat of various farm products.

Heat to Remove for Cooling the Space

• Calculating the heat loss from the surrounding environment.
• Calculating for specific sizes of refrigerated spaces using insulation types.

Rating of Refrigerating System and Rule of Thumb

• Finding the total heat removal required (product and space loads.)
• Formula for Tons of refrigeration: Divide the total heat removal in BTU/hr by 12,000.
• Rule of thumb: The horsepower of a refrigerator system relates directly to the tons of refrigeration. - 1 horsepower = 1 ton of refrigeration (chill rooms) - 2 horsepower = 1 ton of refrigeration (zero-degree rooms)

Sample Calculations

• Sample calculation for walk-in cooler dimensions and products.

Room Air Conditioning

• Types of room air conditioners (console, built-in, and window).
• General size selection recommendations.
• Electrical considerations (individual equipment branch circuit).

Components of Air Conditioner Systems

• Illustrations of condenser, evaporator, and compressor are shown.

Central Air-Conditioning and Heating System

• Diagrams of a central air-conditioning and heating system.

Selection Data for Air Conditioners (HP-Size of Air Conditioners)

• Charts guide proper size selection of air conditioners considering factors like room area, insulation, nighttime operation.

Rule of Thumb for Air Conditioning Design

• A rule of thumb for air conditioning system sizing: 20 square meters of floor space with an 8-foot height at 27°C requires a 1-horsepower air conditioning system.

References

• A list of sources for information about refrigeration.