MCCCD Program Description

System Operating Parameters

Course: HVA255

First Term: 1996 Spring

Lecture 3 Credit(s) 3 Period(s) 3 Load
Subject Type: Occupational
Load Formula: S

Description: Direct expansion evaporators, types and operation. Flooded evaporators, evaporator selection, reciprocating compressor performance, and analysis of systems operation

MCCCD Official Course Competencies
1. Compare and contrast specific types of evaporators. (I) 2. Calculate the capacity of evaporators, the overall conductance factor and the logarithmic mean temperature difference (LTMO). (II) 3. Evaluate the effect of evaporators due to air quantity, surface area, and circulating velocity. (III) 4. Explain the advantages and disadvantages of the direct methods of refrigerant feed. (IV) 5. Evaluate the effect of evaporating temperature difference (TD) on evaporator capacity and humidity. (V) 6. Calculate capacity for natural and forced convected coils. (VI) 7. Select coils for specific application. (VII) 8. Compare and contrast flooded to dry expansion chillers. (VIII) 9. Select chillers for specific applications. (IX) 10. Describe secondary refrigerants. (X) 11. Evaluate the piston displacement, theoretical refrigeration, and actual refrigeration capacity. (XI) 12. Describe the factors that effect the efficiency of a reciprocating compressor. (XII) 13. Explain the operating parameters of refrigeration systems seeking equilibrium. (XIII) 14. Explain methods of cycling refrigeration equipment as load changes. (XIV) 15. Explain methods of capacity control for evaporators and compressors. (XV)
MCCCD Official Course Competencies must be coordinated with the content outline so that each major point in the outline serves one or more competencies. MCCCD faculty retains authority in determining the pedagogical approach, methodology, content sequencing, and assessment metrics for student work. Please see individual course syllabi for additional information, including specific course requirements.

MCCCD Official Course Outline
I. Types of evaporator A. Types 1. Plate 2. Pipe 3. Finned B. Compare c. Contrast II. Evaporator capacity, conductance factor and logarithmic mean temperature difference A. Evaporator capacity B. Conductance factor C. Logarithmic mean temperature difference (LTMO) III. Effect on evaporation A. Air quantity B. Surface are C. Circuiting IV. Refrigerant feed methods A. Methods 1. Dry expansion, also called direct expansion 2. Flooded 3. Liquid overfeed B. Advantages 1. Dry expansion, also called direct expansion 2. Flooded 3. Liquid overfeed C. Disadvantages 1. Dry expansion, also called direct expansion 2. Flooded 3. Liquid overfeed V. Evaporator temperature difference A. Temperature difference (TD) versus capacity B. Temperature difference (TD) versus humidity VI. Coil capacity A. Natural B. Forced VII. Selection of coils A. Calculated load B. Other conditions VIII. Chillers, flooded and dry expansion A. Flooded B. Dry expansion C. Compare D. Contrast IX. Chillers selection A. Chiller load B. Surface area X. Secondary refrigerants A. Define b. Types 1. Brine 2. Antifreeze XI. Piston displacement and refrigerating capacity A. Piston displacement B. Capacity 1. Theoretical 2. Actual XII. Factors that effect compressor efficiency A. Volumetric 1. Compressor clearance 2. Wiredrawing 3. Cylinder heating 4. Valve and piston leapage B. Suction and discharge pressures C. Compression ratio D. Suction temperature E. Discharge temperature F. Compressor power G. Condensing temperature on compressor power H. Actual power I. Water, jacketing the compressor cylinder J. Wet compression K. Suction superheating L. Subcooling XIII. System equilibrium A. System balance B. Graphical analysis C. Evaporator capacity D. Condensing capacity E. System capacity versus calculated load XIV. Load changes A. Temperature B. Pressure 1. Low 2. High 3. Oil C. Pump down cycle XV. Capacity control A. Evaporator 1. Circuiting 2. Air by-pass B. Compressor 1. Unloaders 2. By-pass 3. Multiple compressors.

MCCCD Governing Board Approval Date: 10/24/1995

All information published is subject to change without notice. Every effort has been made to ensure the accuracy of information presented, but based on the dynamic nature of the curricular process, course and program information is subject to change in order to reflect the most current information available.