GATE ME format:nat PYQs & Answers — Page 15 — Exam Papers

Questions 141–150 of 418. Imported answers require independent review unless marked reviewed.

Topic practice 418 questionsPage 15 of 42

Saturated vapor at 200 °C condenses to saturated liquid at the rate of 150 kg/s on the shell side of a heat exchanger (enthalpy of condensation h_fg = 2400 kJ/kg). A fluid with c_p = 4 kJ·kg⁻¹·K⁻¹ enters at 100 °C on the tube side. If the effectiveness of the heat exchanger is 0.9, then the mass flow rate of the fluid in the tube side is ________ kg/s (in integer).

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During open-heart surgery, a patient’s blood is cooled down to 25 °C from 37 °C using a concentric tube counter-flow heat exchanger. Water enters the heat exchanger at 4 °C and leaves at 18 °C. Blood flow rate during the surgery is 5 L/min.

Use the following fluid properties:

Fluid	Density (kg/m )	Specific heat (J/kg-K)
Blood	1050	3740
Water	1000	4200

Effectiveness of the heat exchanger is ________ (round off to 2 decimal places).

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Consider a hydrodynamically and thermally fully-developed, steady fluid flow of 1 kg/s in a uniformly heated pipe with diameter of 0.1 m and length of 40 m. A constant heat flux of magnitude 1500 W/m² is imposed on the outer surface of the pipe. The bulk-mean temperature of the fluid at the entrance to the pipe is 200 °C. The Reynolds number (Re) of the flow is 8500, and the Prandtl number (Pr) of the fluid is 5. The thermal conductivity and the specific heat of the fluid are 0.08 W·m⁻¹·K⁻¹ and 2600 J·kg⁻¹·K⁻¹, respectively. The correlation Nu = 0.023 Re⁰·⁸ Pr⁰·⁴ is applicable, where the Nusselt Number (Nu) is defined on the basis of the pipe diameter. The pipe surface temperature at the exit is ________ °C (round off to the nearest integer).

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Robot Ltd. wishes to maintain enough safety stock during the lead time period between starting a new production run and its completion such that the probability of satisfying the customer demand during the lead time period is 95%. The lead time period is 5 days and daily customer demand can be assumed to follow the Gaussian (normal) distribution with mean 50 units and a standard deviation of 10 units. Using

, where

represents the cumulative distribution function of the standard normal random variable, the amount of safety stock that must be maintained by Robot Ltd. to achieve this demand fulfilment probability for the lead time period is ______ units (round off to two decimal places).

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Consider adiabatic flow of air through a duct. At a given point in the duct, velocity of air is 300 m/s, temperature is 330 K and pressure is 180 kPa. Assume that the air behaves as a perfect gas with constant

kJ/kg.K. The stagnation temperature at this point is ______ K (round off to two decimal places).

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A pressure measurement device fitted on the surface of a submarine, located at a depth

below the surface of an ocean, reads an absolute pressure of 4.2 MPa. The density of sea water is 1050 kg/m

, the atmospheric pressure is 101 kPa, and the acceleration due to gravity is 9.8 m/s

. The depth

is ______ m (round off to the nearest integer).

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Consider an ideal vapour compression refrigeration cycle working on R-134a refrigerant. The COP of the cycle is 10 and the refrigeration capacity is 150 kJ/kg. The heat rejected by the refrigerant in the condenser is ______ kJ/kg (round off to the nearest integer).

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Consider fully developed, steady state incompressible laminar flow of a viscous fluid between two large parallel horizontal plates. The bottom plate is fixed and the top plate moves with a constant velocity of

m/s. Separation between the plates is 5 mm. There is no pressure gradient in the direction of flow. The density of fluid is 800 kg/m

, and the kinematic viscosity is

m

/s. The average shear stress in the fluid is ______ Pa (round off to the nearest integer).

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A rigid tank of volume 50 m³ contains a pure substance as a saturated liquid vapour mixture at 400 kPa. Of the total mass of the mixture, 20% mass is liquid and 80% mass is vapour. Properties at 400 kPa are:

,

m³/kg,

m³/kg. The total mass of liquid vapour mixture in the tank is ______ kg (round off to the nearest integer).

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A rigid insulated tank is initially evacuated. It is connected through a valve to a supply line that carries air at a constant pressure and temperature of 250 kPa and 400 K respectively. Now the valve is opened and air is allowed to flow into the tank until the pressure inside the tank reaches 250 kPa at which point the valve is closed. Assume that the air behaves as a perfect gas with constant properties (

kJ/kg.K,

kJ/kg.K,

kJ/kg.K). Final temperature of the air inside the tank is ______ K (round off to one decimal place).

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