Question

A circular tube part of a heat exchanger is shown below. A hot fluid enters the tube at a temperature $T_{m,i} = 85^circ C$ and a mass flow rate of 10 kg/hr. We can assume that the flow is such that both boundary layers (thermal and velocity) can be considered fully developed. This hot fluid exits the tube at a temperature $T_{m,o} = 40^circ C$. The cooling fluid that circulates around the tube is at $T_{infty} = 25^circ C$. The tube diameter is 1 cm and 1 m long. We can neglect the tube thickness. $T_{infty} = 25^circ C$ $T_{m,o}$ $L = 1 ext{ m},$ $D = 1 ext{ cm}$ $dot{m}$ $T_{m,i} = 85^circ C$ Suddenly, the hot fluid mass flow rate is increased to 30 kg/hr. Find the new fluid exit temperature ($T_{m,o}$). Assume that the external flow is not affected in any way by the change of internal flow conditions. The hot fluid properties are given here : $ ho = 1079 ext{ kg/m}^3$, Cp=2637 J/kg.K, $mu$=0.0034 N.s/m$^2$ and k=0.261 W/m.K

          A circular tube part of a heat exchanger is shown below.

A hot fluid enters the tube at a temperature $T_{m,i} = 85^circ C$ and a mass flow rate of 10 kg/hr. We can
assume that the flow is such that both boundary layers (thermal and velocity) can be considered fully
developed. This hot fluid exits the tube at a temperature $T_{m,o} = 40^circ C$. The cooling fluid that
circulates around the tube is at $T_{infty} = 25^circ C$. The tube diameter is 1 cm and 1 m long. We can neglect
the tube thickness.

$T_{infty} = 25^circ C$
$T_{m,o}$
$L = 1 	ext{ m},$
$D = 1 	ext{ cm}$
$dot{m}$
$T_{m,i} = 85^circ C$

Suddenly, the hot fluid mass flow rate is increased to 30 kg/hr.

Find the new fluid exit temperature ($T_{m,o}$). Assume that the external flow is not affected in any way
by the change of internal flow conditions.

The hot fluid properties are given here :
$
ho = 1079 	ext{ kg/m}^3$, Cp=2637 J/kg.K, $mu$=0.0034 N.s/m$^2$ and k=0.261 W/m.K

A circular tube part of a heat exchanger is shown below.

A hot fluid enters the tube at a temperature Tm,i = 85^circ C and a mass flow rate of 10 kg/hr. We can
assume that the flow is such that both boundary layers (thermal and velocity) can be considered fully
developed. This hot fluid exits the tube at a temperature Tm,o = 40^circ C. The cooling fluid that
circulates around the tube is at Tinfty = 25^circ C. The tube diameter is 1 cm and 1 m long. We can neglect
the tube thickness.

Tinfty = 25^circ C
Tm,o
L = 1 ext m,
D = 1 ext cm
dotm
Tm,i = 85^circ C

Suddenly, the hot fluid mass flow rate is increased to 30 kg/hr.

Find the new fluid exit temperature (Tm,o). Assume that the external flow is not affected in any way
by the change of internal flow conditions.

The hot fluid properties are given here :
ho = 1079 ext kg/m^3, Cp=2637 J/kg.K, mu=0.0034 N.s/m^2 and k=0.261 W/m.K

Added by John L.

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