HRAC 211 Lab 03 - Cooling Trainer - Plotting Performance

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Centennial College *

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211

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Mechanical Engineering

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Jan 9, 2024

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Centennial College HRAC 211 Psychrometrics and Controls Name (Please Print): Student Number: Class Number: Date: Received by Inst.: Overview - Lab 3 – Psychrometric Data To accurately assess a Mechanical / Electrical systems performance, we must learn to collect its Key Performance Indicating values. Like a Medical Doctor collects their patients’ blood pressure, weight, height, and then conduct a discussion on the patients’ general feelings. As an HRAC Doctor , you the technician will need to learn how to determine amongst such things as, a systems actual net refrigeration effect (NRE), its overall system performance as compared to energy consumption costs, and compare those findings to all “feeling’s of comfort people experience”, or, whatever the design criteria of the M&E system is suppose to be - as set by the manufacturer. In short, we’re the go to people when a client wants to know if their system is delivering its optimum performance, efficiently. Today’s Lab is challenging as we need to collect this specific data as accurately as possible, make our calculations correctly, plot out our findings as proof, and then offer our recommendations, if any are required in a professional manner. Objective: To gather and record operational characteristic data associated with a basic RAC system. Once the data is calculated determine the Net Refrigeration Effect (NRE) and graph the results on a psychrometric chart. Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
Materials Required: 1 Refrigeration demonstrator 1 Electronic Psychrometer or manual sling Psychrometer 1 Clamp-on amp meter 1 Anemometer Psychometric Chart’s (as needed) Caution: Work In A Team Consisting of a Maximum Of 4 Students. You must be wearing approved PPE or access to the Lab is denied. Today’s Challenge’s Are: 1. Set the HRAC demonstrator for Cooling. For metering device - select the capillary tube. 2. For Part “A”, set the evaporator fan damper to the letter specified in the data chart. Condenser should be set to “1” 3. For Part “B”, set the condenser fan to the number indicated in the data chart. Evaporator should be set to “A” 4. Use the anemometer to determine the velocity of the air leaving the coil. Use the charts on page 4 of this lab. In part “A” this will be the evaporator, in “B” this will be the condenser. Average the velocity readings and record in the chart. Next, take that average air velocity reading and multiply it by the square surface of the evaporator. Finally, multiply that number by a factor of 80%. Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
Before you do this, you must calculate your evaporator area properly. (For Example: The Trainer Evaporator surface measures 10” x 12” = 120 square inches. You must then convert this figure into square feet. So - you must divide 120” Square Inches by 144 square inches = 0.83 square feet. Next… Use 0.83 x your average velocity readings, say in this example, the number 820 is used. - therefore .83 x 820 = 683.3 - Now continue with your final equation using a factor of 80% to find the Cubic Feet per Minute (CFM) of air leaving the condenser. - For example, 683.3 x .80% = 546.6 CFM Note: This will have to be done each time the damper is changed on the fan. 5. Take the stabilized temperature reading of the air entering the fan housing. Record the data. Take the stabilized temperature reading of the air leaving the coil. Record data. Record the voltage and amperage of the fan motor and record data. 6. Change the damper position to the next position and repeat 4 & 5 until data for “A” and “B” are completed. 7. Repeat the procedure for the condenser with the evaporator damper set to “A” 8. Your lab must be signed off on completion by the instructor. Data in your lab will be used for the Week 4 lecture. Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
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Notes Performance Observations & Data Collection: 1. Observations Evaporator (Condenser damper set at “1”) Damper Position Fan Motor Volts Fan Motor Amps Velocity 1 Velocity 2 Velocity 3 Average Velocity CFM Inlet wb Inlet db Outlet wb Outlet db A B C 2. Observations Condenser (Evaporator damper set at “A”) Damper Position Fan Motor Volts Fan Motor Amps Velocity 1 Velocity 2 Velocity 3 Average Velocity CFM Inlet wb Inlet db Outlet wb Outlet db 1 2 3 Questions: Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
1. What is the relationship between temperature rise (T), air flow (CFM) and capacity (BTU/hr)? 2. What is the relationship between heat differential (Q), air flow (CFM) and capacity (BU/hr)? 3. Will a draft of 75 F feel cold, cool, warm or hot when it impinges on someone? 4. Find the human comfort chart. Do you agree with the temperatures and humidity on it? Why? Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
5. Using the following data from Environment Canada, find the wet bulb temperature for each row: Conditions Temp (°F) Humidity (%) Dew Point (°F) Wind (mph) Pressure (inches) Visibility (miles) Wet Bulb Haze 58 85 53 calm 30.1 6 Mainly Clear 55 84 50 NNE 4 30.1 15 Partly Cloudy 68 45 46 SSE 12 30.1 15 Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved
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Marking: Marking Items Maximum points Mark Practical and Observations 20 Questions and/or Research 20 Clean up, Return tools, materials and equipment to their proper locations 5 Safety Precautions (goggles, gloves and safety boots) 5 Late Submission ̽ One Week - Lose 15 Two Weeks Lose 50 Total mark 50 Professor’s name ------------------------------------------------------- Notes: ̽̽ The deadline for the lab report submission, unless altered by the Instructor, is at the end of the Lab. For example, Lab 2a and 2b is due at the conclusion of Lab 2b. Lab 3 is due at the end of Lab 3. If handed in at the beginning of next weeks Lab, one week after your Lab session - deduct 15 marks. Lab Reports will NOT be accepted after the end of the following weeks lab time and the Lab will be given an evaluation of ZERO. Student Signature __________________________________________________________________________________ Student Printed name _____________________________________________ Resources Chapter / Unit 35 and 16 9 th Edition Refrigeration & Air Conditioning Technology. Authors: Eugene Silberstein, Jason Obrzut, John Tomczyk, Bill Whitman, Bill Johnson ISBN – 13: 978-0-357-12227-3 Property of Centennial College – SETAS/SDRE/HRAC Programs, Copyright Protected 2020, All Rights Reserved