View
66
Download
5
Category
Tags:
Preview:
DESCRIPTION
CHAPTER. Truck-Trailer Refrigeration Equipment. 13. Instructor Name: (Your Name ). Learning Objectives. Describe air circulation through the cargo area. List three different forms of short cycling. Explain the operation of the thermostat. Describe the refrigeration unit operation. - PowerPoint PPT Presentation
Citation preview
Copyright © 2014 Delmar, Cengage Learning
Truck-Trailer Refrigeration Equipment
Instructor Name: (Your Name)
13CHAPTER
Copyright © 2014 Delmar, Cengage Learning
Learning Objectives
Describe air circulation through the cargo area. List three different forms of short cycling. Explain the operation of the thermostat. Describe the refrigeration unit operation. Explain the reasons for pre-cooling trucks and
trailers. Explain loading procedures to ensure proper
circulation .
Copyright © 2014 Delmar, Cengage Learning
Learning Objectives (continued)
Describe cargo floor construction. Explain a pre-trip inspection. Describe the advantages of multi-temperature
refrigeration units.
Copyright © 2014 Delmar, Cengage Learning
Trailer Refrigeration Unit
Copyright © 2014 Delmar, Cengage Learning
System Components
Engine- Typically a four cylinder diesel. Compressor- Range from 2 to 4 cylinder. Condenser- Dissipates heat from trailer to ambient
air. Thermostatic Expansion Valve- Fixed orifice,
externally equalized. Evaporator- Absorbs heat in the trailer. Microprocessor- Brain of unit. Controls all aspects
of refrigeration and heating process.
Copyright © 2014 Delmar, Cengage Learning
Typical Refrigeration Engine and Microprocessor
Copyright © 2014 Delmar, Cengage Learning
System Components (continued)
Box Temperature- The actual temperature in the storage unit.
Set Point- Optimum temperature to maintain product.
Thermostat- Sets the temperature that the equipment will maintain.
Refrigerant- Chemical used to absorb and dissipate heat in the storage area.
Copyright © 2014 Delmar, Cengage Learning
Trailer Refrigeration System Layout
Copyright © 2014 Delmar, Cengage Learning
Trailer floor Construction
Fabricated from Aluminum
Forms ductwork under cargo for air circulation
Must be kept free from debris that can impede air flow
Copyright © 2014 Delmar, Cengage Learning
Multi Temperature Refrigeration Units May have up to three units. Each unit has its own evaporator and
thermostat. Unit can store fresh, frozen and dry goods
together.
Copyright © 2014 Delmar, Cengage Learning
Multi Temperature Trailer
Copyright © 2014 Delmar, Cengage Learning
Pre Cooling Products
Product must be cooled to the holding temperature prior to loading trailer.
Trailer refrigeration equipment is designed to maintain temperature of product not cool it down.
Pre cool the trailer prior to loading. Shut down refrigeration unit while loading to
prevent refrigerated air from escaping.
Copyright © 2014 Delmar, Cengage Learning
Proper Loading Procedures• Pallets must be loaded so skids allow air flow
fore and aft in trailer.• Product must be kept away from walls to allow
air flow around all sides.• Ample air space must be allowed between load
and ceiling.• Air space must be left between cargo door and
cargo.• Air space must be left between front bulkhead
and cargo.
Copyright © 2014 Delmar, Cengage Learning
Proper Pallet Placement
Copyright © 2014 Delmar, Cengage Learning
Proper Cargo Loading Technique
Copyright © 2014 Delmar, Cengage Learning
Improper Loading of Cargo
Copyright © 2014 Delmar, Cengage Learning
Short Cycling Cargo is blocking units discharge air flow. Cold air is routed back to air inlet. Thermostat thinks it has reached set point and
switches to heat mode. Warm air flow is blocked and routed back to air
inlet. Thermostat thinks it has reached set point and
switches to cool mode. Process continues over and over, “Short
Cycling.”
Copyright © 2014 Delmar, Cengage Learning
Auto Stop/Start Auto stop/start used by most equipment today. Constant run mode still available. Constant run mode, unit cycles between heat and
cool mode. Auto stop/start mode, unit will shut down once set
point is reached and programmed parameters are met.
Programmed parameters- unit must run long enough to charge battery and warm the engine.
Unit stays off until box temperature reaches preset temperature.
Copyright © 2014 Delmar, Cengage Learning
Summary
Microprocessors control all aspects of refrigeration and heating cycles.
Modern advances in technology allow distribution to market fresh fruit and vegetables any time of year.
Loads must be pre cooled to remove residual heat and humidity.
The box must be pre cooled to remove residual heat and humidity.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)
Correct loading is essential to product quality. Discharge air must be able to circulate freely
around all side of the product. Rising fuel costs have contributed to the
technology for auto stop/start. The auto stop/start feature is a huge financial
savings for the company using it , as well as a way of conserving our natural resources.
Recommended