A mixture of chemicals is flowing in a pipe ( k = 14 W/m .K, D i =2 .5 cm, D o =3 cm and L= 10 m) . and During the transport. the mixture undergoes an exothermic reaction having an average temperature of 135°C and a convection heat transfer coefficient of 150 W/m 2 K. To prevent any incident of thennal burn, the pipe needs to be insulated. However, due to the vicinity of the pipe, there is only enough room to fit a 2.5-cm-thick layer of insulation over the pipe. The pipe is situated in a plant where the average ambient air temperature is 20°C and the convection heat transfer coefficient is 25 Win2K. Determine the insulation for the pipe such that the thermal conductivity of the insulation is sufficient to maintain the outside surface temperature at 45°C or lower.
A mixture of chemicals is flowing in a pipe ( k = 14 W/m .K, D i =2 .5 cm, D o =3 cm and L= 10 m) . and During the transport. the mixture undergoes an exothermic reaction having an average temperature of 135°C and a convection heat transfer coefficient of 150 W/m 2 K. To prevent any incident of thennal burn, the pipe needs to be insulated. However, due to the vicinity of the pipe, there is only enough room to fit a 2.5-cm-thick layer of insulation over the pipe. The pipe is situated in a plant where the average ambient air temperature is 20°C and the convection heat transfer coefficient is 25 Win2K. Determine the insulation for the pipe such that the thermal conductivity of the insulation is sufficient to maintain the outside surface temperature at 45°C or lower.
Solution Summary: The author calculates the thickness of insulation around the pipe. The conductivity of the insulation is 0.32 W/mK.
A mixture of chemicals is flowing in a pipe
(
k
=
14
W/m
.K,
D
i
=2
.5 cm, D
o
=3 cm and L= 10 m)
.
and During the transport. the mixture undergoes an exothermic reaction having an average temperature of 135°C and a convection heat transfer coefficient of 150 W/m2 K. To prevent any incident of thennal burn, the pipe needs to be insulated. However, due to the vicinity of the pipe, there is only enough room to fit a 2.5-cm-thick layer of insulation over the pipe. The pipe is situated in a plant where the average ambient air temperature is 20°C and the convection heat transfer coefficient is 25 Win2K. Determine the insulation for the pipe such that the thermal conductivity of the insulation is sufficient to maintain the outside surface temperature at 45°C or lower.
Calculate the entropy increase in the evaporation of one mole of water at 100 °C. Heat of vaporization of water at 100 °C = 2259.4 J g-1.
Steam of 1.4MN/m2 and of dryness fraction 0.7 is throttled to 0.11MN/m2 determine the dryness fraction of the steam after throttling?
An evaporator is used to concentrate 4536 kg/hr (10,000 lb/h) of a 20% solution of NaOH in water entering at 600C (1400F) to a product of 50% solids. The pressure of the saturated steam used is 172.3 kPa (25 psia) and the pressure of the vapor phase in the evaporator is 11.7 kPa (1.7 psia). The overall heat transfer coefficient is 1560 W/m2-K (275 BTU/h-ft2 – 0F). Calculate for the steam used, steam economy, and heating surface area.
Required: ____________, _____________, _______________
Solution:1. Calculate the amounts of the L and V phase products using the material balance equations.2. From steam tables the boiling point of pure water at 11.7 kPa is _____________3. From the HANDBOOK Chart the boiling point rise is _______________ and consequently the boiling point of the solution is _______________4. From the enthalpy-concentration chart of NaOH in the Handbook the enthalpy of the feed is _____________ and the enthalpy of the liquid product is _______________.5. From steam tables…
Chapter 3 Solutions
Heat and Mass Transfer: Fundamentals and Applications
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