# Recent questions tagged heat-exchanger

In a concentric tube counter-flow heat exchanger, hot oil enters at $102^{\circ}C$ and leaves at $65^{\circ}C$. Cold water enters at $25^{\circ}C$ and leaves at $42^{\circ}C$. The log mean temperature difference $(LMTD)$ is ________ $^{\circ}C$ (round off to one decimal place).
Hot and cold fluids enter a parallel flow double tube heat exchanger at $100^{\circ}C$ and $15^{\circ} C$, respectively. The heat capacity rates of hot and cold fluids are $C_h=2000 \: W/K$ and $C_c =1200 \: W/K$, respectively. If the outlet temperature of ... is $45^{\circ} C$, the log mean temperature difference (LMTD) of the heat exchanger is __________ $K$ (round off to two decimal places).
In a counter-flow heat exchanger, water is heated at the rate of $1.5 \: kg/s$ from $40^{\circ}$ C to $80^{\circ} \: C$ by an oil entering at $120^{\circ}$ C and leaving at $60 ^{\circ}$ C. The specific heats of water and oil are $4.2 \: kJ/kg.K$ ... heat transfer coefficient is $400 W/m^{2}.K$. The required heat transfer surface area (in $m^{2}$) is $0.104$ $0.022$ $10.4$ $21.84$
A cylindrical steel rod, $0.01 \: m$ in diameter and $0.2 \: m$ in length is first heated to $750^ \circ C$ and then immersed in a water bath at $100^ \circ C$. The heat transfer coefficient is $250 \: W/m^2-K$. The density, specific heat and thermal conductivity of steel ... $k=43 \: W/m-K$, respectively. The time required for the rod to reach $300^ \circ C$ is ________ seconds.
For a heat exchanger, $\triangle T_{\text{max}}$ is the maximum temperature difference and $\triangle T_{\text{min}}$ is the minimum temperature difference between the two fluids. LMTD is the log mean temperature difference. $C_{\text{min}}$ and $C_{\text{max}}$ are the minimum and the ... $C_{\text{max}} \triangle T_{\text{max}}$ $C_{\text{max}} \triangle T_{\text{min}}$
Consider a parallel-flow heat exchanger with area $A_p$ and a counter-flow heat exchanger with area $A_c$ . In both the heat exchangers, the hot stream flowing at $1 \: kg/s$ cools from $80^\circ C$ to $50^\circ C$. For the cold stream in both ... heat exchangers are of the same fluid. Also, both the heat exchangers have the same overall heat transfer coefficient. The ratio $A_c/A_p$ is _________
Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is $R_o$ and that of the inner cylinder is $R_i$ . The radiation view factor of the outer cylinder onto itself is $1-\sqrt{\dfrac{R_i}{R_o}}\\$ $\sqrt{1-\dfrac{R_i}{R_o}} \\$ $1-\dfrac{R_i}{R_o}^{1/3} \\$ $1-\dfrac{R_i}{R_o}$
A plane wall has a thermal conductivity of $1.15$ $W/m.K$. If the inner surface is at $1100^{\circ} C$ and the outer surface is at $350^{\circ} C$, then the design thickness (in meter) of the wall to maintain a steady heat flux of $2500$ $W/m^2$ should be _______
A double-pipe counter-flow heat exchanger transfers heat between two water streams. Tube side water at $19$ liter/s is heated from $10^{\circ} \: C$ to $38^{\circ} \: C$. Shell side water at $25$ $litre/s$ is entering at $46^{\circ} \: C$. Assume constant properties of water; density is $1000 \: kg/m^3$ and specific heat is $4186 \: J/kg.K$. The LM TD (in $^{\circ}C$) is _______
An amount of $100 \: kW$ of heat is transferred through a wall in steady state. One side of the wall is maintained at $127^{\circ} \: C$ and the other side at $27^{\circ} \: C$. The entropy generated (in $W/K$) due to the heat transfer through the wall is _______
In a heat exchanger, it is observed that $ΔT_1$ = $ΔT_2$, where $ΔT_1$ is the temperature difference between the two single phase fluid streams at one end and $ΔT_2$ is the temperature difference at the other end. This heat exchanger is a condenser an evaporator a counter flow heat exchanger a parallel flow heat exchanger