Page 53 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

There are two methods of interpolation:

i. single interpolation

ii. double interpolation

i. Single interpolation

Single interpolation is used to find the values in the table when one of the values is not

tabulated. For example, to find the saturation temperature, specific volume, internal

energy and enthalpy of dry saturated steam at 77 bar, it is necessary to interpolate
between the values given in the table.

Example 2.6

Determine the saturation temperature at 77 bar.

Solution to Example 2.6

The values of saturation temperature at a pressure of 77 bars are not tabulated in the
Steam Tables. So, we need to interpolate between the two nearest values that are

tabulated in the Steam Tables.

t − 290 5 . 295 − 290 5 .
s =
P 77 − 75 80 − 75

80
t − 290 5 . 295 − 290 5 .
s =
77
2 5
75

t = 2 ( 5.4 ) + 290 5 .
ts s 5
290.5 ts 295
o
ts = 292.3 C

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