Problem $09\mathrm{.}156-$ A Horizontal Copper Tube Enclosed in a Concentric Thin Glass Tube

A solar collector consists of a horizontal copper tube of outer diameter $7$ cm enclosed in a concentric thin glass tube of $13$ cm diameter. Water is heated as it flows through the tube, and the annular space between the copper and glass tube is filled with air at $1$ atm pressure. During a clear day, the temperatures of the tube surface and the glass cover are measured to be $60C$ and $32C,$ respectively. Determine the rate of heat loss from the collector by natural convection per meter length of the tube.

The properties of air at $1$ atm and the average temperature of $\frac{T_i+T_0}{2}=\frac{60+32}{2}=46C$ are $k=0\mathrm{.}02706\frac{W}{m}*C,v=1\mathrm{.}760{10}^{-5}\frac{m^2}{s},Pr=0\mathrm{.}7238,$ and $=0\mathrm{.}003135K^{-1}$

$$

The rate of heat loss from the collector by natural convection per meter length of the tube is $25\mathrm{.}167.$ W $.$

Problem $09\mathrm{.}156-$ A Horizontal Copper Tube Enclosed in a Concentric Thin Glass Tube

A solar collector consists of a horizontal copper tube of outer diameter $7$ cm enclosed in a concentric thin glass tube of $13$ cm diameter. Water is heated as it flows through the tube, and the annular space between the copper and glass tube is filled with air at $1$ atm pressure. During a clear day, the temperatures of the tube surface and the glass cover are measured to be $60C$ and $32C,$ respectively. Determine the rate of heat loss from the collector by natural convection per meter length of the tube.

The properties of air at $1$ atm and the average temperature of $\frac{T_i+T_0}{2}=\frac{60+32}{2}=46C$ are $k=0\mathrm{.}02706\frac{W}{m}*C,v=1\mathrm{.}760{10}^{-5}\frac{m^2}{s},Pr=0\mathrm{.}7238,$ and $=0\mathrm{.}003135K^{-1}$

$$

The rate of heat loss from the collector by natural convection per meter length of the tube is $25\mathrm{.}167$

$$ W$.$