Ahorizontal pipe 15 cm in diameter and 4 m long is buried in the earth at a depth of 20 cm. the pipe-wall temperature is 75 degree c and the earth surface temperature is 5 degree c. assuming that the thermal conductivity of the earth is 0.8w/m. degree c. calculate the heat lost by the pipe. what is the heat lost if the pipe was buried at a depth of 180 cm?

Explanation:

The given data for case (1) is as follows.

  h = 20 cm = 0.2 m

Assuming that a rectangular slab is placed above the pipe and we will calculate the heat transfer as follows.

              Q =

  where,    A = area

                  L = length

                  k = thermal conductivity = 0.8 W/m

              = change in temperature.

Therefore, putting the given values into the above formula as follows.

            Q =

                =

                = 168 W

For case (2), h = 180 cm = 1.8 m

Therefore, heat lost will be calculated as follows.

                       Q =

                           =

                           = 18.67 W

Thus, we can conclude that 18.67 W heat lost if the pipe was buried at a depth of 180 cm.

the ratio of the conjugate base to the acid required to attain the desired ph.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.