Specifications

Ver SG 9/200 10 Sharp Electronics Corporation
One pound of food with 50% moisture will take less time to heat to a specific temperature
than one pound of food with 75% moisture. Or if both are heated for the same length of
time, the former will reach a higher temperature than the latter. One pound of water,
however, will heat only half as fast as one pound of fat. The reason for this requires an
explanation of the term specific heat. This is a measure of a material’s ability to hold
heat as compared to water. Water has a value of one (1.0). Fats are about 0.5. Thus
water takes twice as much heat as fat to increase its temperature by one degree.
Therefore in our one kilowatt oven, one pound of fat will increase in temperature by
114°F, however, the same amount of water will only increase 57°F. (It should be noted
that this does not apply at high temperatures where some of the water may be changed to
steam. This change uses up much more energy.)
A simple formula shows the relationship between the heat required and these other
factors:
“Heat required (BTU) equals Weight (lbs.) times specific heat times
temperature difference (°F.)”
Q = W x s x t
Here’s an example:
How long would it take to heat 12 ounces of canned green beans to 160°F. in a one
kilowatt microwave oven? The specific heat of most vegetables because of their high
moisture content is around 0.9. Let us assume that the beans would be at an initial
temperature of about 70°F.
Q = 0.75? lbs. x 0.9 x (160°F. - 70°F.)
Q = 60.75 BTU
Since our oven (1 kW) provided 57 BTU per minute, then the heat required (Q) divided
by 57 BTU/minute would give the time.
60.75/57.0 = about 1 minute 3 seconds
How long would it take if the green beans were just removed from a 40°F. refrigerator?
Q = 0.75 lbs. X 0.9 x (160°F. - 40°F.)
Q = 81
Time = 81/57 = about 1.5 minutes
When two foods at different starting temperatures are heated simultaneously in a
microwave oven the colder food takes longer than the warmer food. An interesting
example is that of apple pie and ice cream. With the pie at room temperature and a scoop
of hard frozen ice cream on top, the pie can be warmed without melting the ice cream.
About 15 seconds in a 1 kW oven will do the trick.