Pasco TD-8564 THERMAL EFFICIENCY APPARATUS Manuel d'utilisateur télécharger pdf (Page 15)

012-05443A Thermal Efficiency Apparatus

Analysis and Questions

To compare the actual efficiency to the Carnot efficiency, construct a graph.

Plot the Carnot efficiency vs. ∆T and also plot the actual efficiency vs. ∆T. This may be

done on the same graph.

➤ NOTE: We are assuming by doing this that T

was nearly constant.

➀ The Carnot efficiency is the maximum efficiency possible for a given temperature differ-

ence. According to the graph, is the actual efficiency always less than the Carnot effi-

ciency?

➁ Does the Carnot efficiency increase or decrease as the temperature difference increases?

➂ Does the actual efficiency increase or decrease as the temperature difference increases?

➃ The Carnot efficiency represents the best that a perfect heat engine can do. Since this heat

engine is not perfect, the actual efficiency is a percentage of the Carnot efficiency. The

overall (actual) efficiency of a real heat engine represents the combination of the engine’s

ability to use the available energy and the maximum energy available for use. From the data

taken, what is the percentage of available energy used by this heat engine?

➄ The actual efficiency of this heat engine is very low and yet heat engines of this type are

used extensively in remote areas to run things. How can such an inefficient device be of

practical use?

Table 1.2 Calculated Values

Trial P

(k) T

(k) ∆T (k) e

actual

Carnot

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 33 34

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Pasco TD-8564 THERMAL EFFICIENCY APPARATUS Manuel d'utilisateur Page 15