HEATING TUTORIAL INSTRUCTIONS

Open the tutorial.xls Excel Workbook which is in the Hort4050 directory. Select the HEATING worksheet. This is a spreadsheet which allows you to enter information that is needed in order to calculate the heating requirements for three types of greenhouses. As you calculate the heating requirements for the examples below, think about the limitations of our heating requirement model. What information is missing from our examples that is needed to accurately estimate heat loss from these greenhouses? We'll discuss this in greater detail during the semester. For each of the greenhouse situations described below find the appropriate information in the tables in Chapter 3 of your textbook and enter this into the spreadsheet. Record the answers in the appropriate spaces on this instruction sheet.

Take note of:

1. the impact of shifts in greenhouse situations on the heat requirement and
2. the speed and ease of conducting a cost analysis of heating when you use a computer.

A. A-FRAME GREENHOUSE

1. The heat requirement (MBtu/hr) for the A-frame greenhouse described below is __________.

    

   
   • average wind velocity: 15 mph
   • minimum outside temperature: 10 °F
   • inside temperature: 60 °F
   • greenhouse construction: all-metal frame with tight glass
   • curtain wall construction: 4 inch thick concrete

    

2. How much more heat would be required if the above greenhouse was located along the North Carolina coast where there was an average wind velocity of 25 mph? __________

    

3. How would the heat requirement differ if this same greenhouse frame was covered with FRP (fiberglass) rather than glass? __________

B. QUONSET GREENHOUSE

1. The heat requirement for the following metal frame double polyethylene covered quonset greenhouse is __________. All other conditions are the same as in exercise A1.

    

   
2. How much more heat would be required per hour if the night temperature inside the greenhouse was raised up to 70 °F to meet the requirements of an African violet crop? __________

    

3. How much would the heat requirement rise if only one layer of polyethylene was applied to this greenhouse? __________

C. GUTTER-CONNECTED GREENHOUSE

1. The heat requirement for the following metal frame, double polyethylene covered gutter-connected greenhouse is __________. The environmental conditions are the same as in exercise A1. There is no curtain wall. Round up the wall length from 368 to 370 feet.

    

   
2. How much would the heat requirement rise in the above gutter-connected greenhouse if the side walls were 2 feet higher? __________

    

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