Chapter 5 · MCQ Read Mode

Energy and Heat Transfer

Which of the following is a renewable but conventional source of energy?

Hydrogen is best described as

Which rank of coal has the highest carbon content and calorific value?

The proximate analysis of a coal reports

The gross calorific value of a fuel is always greater than its net calorific value because

The mass of oxygen theoretically required to burn 1 kg of carbon completely to carbon dioxide is

In the Orsat apparatus, the gases are absorbed in the order

Supplying a large excess of air to a furnace

For a high-head, low-flow hydropower site, the most suitable turbine is

Gasification differs from combustion in that gasification

The chief constituent of biogas produced by anaerobic digestion is

A fuel cell is more efficient than a conventional thermal power plant principally because

In the electrolysis of water, the gases liberated at the cathode and anode respectively are

The negative sign in Fourier's law of heat conduction indicates that

The thermal resistance of a hollow cylinder of inner radius r1 and outer radius r2 is

In a composite wall, the largest temperature drop occurs across the layer with

Thermal diffusivity is defined as

The critical radius of insulation for a cylindrical pipe is given by

Adding insulation to a small-diameter electrical wire whose radius is below the critical radius will

For a plane wall, the critical thickness of insulation

Fin efficiency is defined as the ratio of the actual heat transferred by the fin to the heat that would be transferred if

Fins are most effective when added to a surface in contact with

The Biot number represents the ratio of

The lumped capacitance method for unsteady conduction may be applied when the Biot number is

In the lumped capacitance model, the temperature of a body approaches that of its surroundings

Most common insulating materials owe their low thermal conductivity to

The convective heat transfer coefficient h is

The Nusselt number represents the ratio of

The Prandtl number of a fluid is

For fully developed laminar flow in a tube with constant wall temperature, the Nusselt number is

In the Dittus-Boelter equation, the exponent on the Prandtl number is

According to the Dittus-Boelter equation, doubling the velocity in a tube increases the heat transfer coefficient by a factor of about

In natural convection, the Reynolds number is replaced by the

For turbulent natural convection, where the Nusselt number varies as the Rayleigh number to the power one third, the heat transfer coefficient is

The critical heat flux in pool boiling corresponds to

In the transition boiling regime, as the excess temperature is increased the heat flux

Dropwise condensation gives a higher heat transfer coefficient than filmwise condensation because

The presence of a small amount of non-condensable gas in a condenser

Condenser tubes are usually arranged horizontally rather than vertically because

According to the Stefan-Boltzmann law, the emissive power of a black body is proportional to

The value of the Stefan-Boltzmann constant is approximately

Wien's displacement law states that as the temperature of a body increases, the wavelength of maximum emission

Kirchhoff's law of radiation states that at thermal equilibrium

For an opaque surface, the sum of absorptivity and reflectivity is

A grey body is one whose

Which of the following surfaces has the lowest emissivity?

The view factor between two surfaces depends on

For a flat or convex surface, the view factor with respect to itself, F11, is

For a small grey body of emissivity e1 completely enclosed by a much larger surface, the net radiant exchange depends on

For radiation exchange between two large parallel grey plates, the denominator of the exchange expression is

Inserting a single radiation shield of the same emissivity between two large parallel plates reduces the radiant heat transfer to

Which pair of gases is essentially transparent to thermal radiation?

The logarithmic mean temperature difference is

For the same four terminal temperatures, the LMTD for counter-current flow compared with co-current flow is

A temperature cross, in which the hot fluid leaves colder than the cold fluid outlet, is possible only in

In the expression q = UAF(ΔT)lm, the correction factor F is

The primary function of baffles in a shell-and-tube heat exchanger is to

A floating-head design is used in a shell-and-tube heat exchanger in order to

A square tube pitch is preferred over a triangular pitch when

In a heat exchanger, the overall heat transfer coefficient is governed principally by

The effectiveness of a heat exchanger is defined as the ratio of the actual heat transfer to

The effectiveness-NTU method is preferred over the LMTD method when

When one fluid in a heat exchanger is condensing at constant temperature, the capacity ratio Cr is

The fouling factor in a heat exchanger calculation represents

The commonest operational cause of fouling in a heat exchanger is

The economy of an evaporator is defined as

Increasing the number of effects in a multiple-effect evaporator

The approximate steam economy of a triple-effect evaporator is

In backward-feed operation of a multiple-effect evaporator

Parallel feeding of a multiple-effect evaporator is used principally when

Boiling point elevation in an evaporator has the effect of

A forced-circulation evaporator is most suitable for

A falling-film evaporator is particularly suitable for heat-sensitive materials because

In the batch heating of an agitated vessel by condensing steam in the jacket, the contents approach the steam temperature

In batch heating of an agitated vessel, doubling the heat transfer area will

Compared with a jacket, an internal helical coil in a reactor generally provides

The vessel-side heat transfer coefficient in an agitated jacketed reactor is correlated against

Temperature control becomes more difficult as a batch reactor is scaled up because