To find the average or 'mean transmission surface', first calculate the square feet of exterior dimensions, then measure the total square feet inside by measuring the interior surface. The average of these two surfaces is the mean transmission surface. To determine the weight of ice melted, weigh the empty water pan at the start and end of a 24-hour test, deducting the initial weight to find the difference. For temperature tests, ensure the refrigerator is in a room free from drafts with even temperatures, without food inside or door openings during testing. The refrigerator should be thoroughly chilled for at least 48 hours before testing. Place a thermometer in the center of the food chamber and take readings every three hours. Take room temperature simultaneously. Average all food and outside room temperatures to find their difference using the formula: I = 144 X S (T - t), where I is ice melted, 144 is B.t.u. required to melt one pound of ice, S is mean transmission surface, T is average room temperature, t is average temperature of food chamber, and X is number of B.t.u.'s passing through one square foot of surface per degree Fahrenheit temperature difference.
<Callout type="important" title="Thorough Testing">Ensure the refrigerator has been chilled for at least 48 hours before testing to get accurate results.</Callout>
<Callout type="warning" title="Avoid Drafts">Place the refrigerator in a room free from drafts and with even temperatures to prevent inaccurate readings.</Callout>
Key Takeaways
- Calculate the mean transmission surface by averaging exterior and interior square feet.
- Weigh ice melted over a 24-hour period to determine efficiency.
- Use specific formula to calculate B.t.u. transmission.
Practical Tips
- Ensure accurate temperature readings by avoiding drafts and maintaining even room temperatures.
- Thoroughly chill the refrigerator for at least two days before testing.
- Take multiple food chamber temperature readings over a period of time.
Warnings & Risks
- Do not open doors during tests to avoid inaccurate results.
- Place the thermometer in the center of the food chamber for accurate readings.
- Avoid placing the refrigerator near sources of heat or cold drafts.
Modern Application
While this chapter focuses on testing refrigerators from a historical perspective, its principles remain relevant today. Understanding how to measure efficiency and B.t.u. transmission can help in assessing modern appliances' performance and energy consumption. This knowledge is crucial for optimizing resource use during survival scenarios.
Frequently Asked Questions
Q: How do you calculate the mean transmission surface?
To find the mean transmission surface, first measure the square feet of exterior dimensions and then measure the total square feet inside by measuring the interior surface. The average of these two surfaces is the mean transmission surface.
Q: What formula is used to determine B.t.u. transmission?
The formula I = 144 X S (T - t) is used, where I represents ice melted, 144 is the B.t.u. required to melt one pound of ice, S is mean transmission surface, T is average room temperature, and t is average temperature of food chamber.
Q: Why should the refrigerator be chilled for at least 48 hours before testing?
Chilling the refrigerator thoroughly for at least two days ensures accurate results by allowing it to reach a stable operating condition.