Chapter 9 · MCQ Read Mode

Heat Transfer, Energy Resources and Environment

Heat transfer by radiation:

Fourier's law of heat conduction is:

Which material has the highest thermal conductivity?

Heat flow through a 0.2 m thick wall of area 10 m² with k = 1 W/mK and a temperature difference of 20 °C is:

The thermal resistance of a hollow cylinder of length L is:

The critical radius of insulation for a cylindrical pipe is:

Lumped-system analysis of transient conduction is valid when the Biot number is:

If the absolute temperature of a black body is doubled, its emissive power becomes:

According to Wien's displacement law, λmaxT equals about:

For an opaque body:

Kirchhoff's law of radiation states that at thermal equilibrium:

For a plane wall between two fluids, the overall heat transfer coefficient U is given by:

Natural (free) convection is caused by:

The dimensionless number that governs free convection is the:

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

Dropwise condensation compared to filmwise condensation gives:

Fins are most effective when attached to the side having:

Fin effectiveness increases with:

The efficiency of a fin with an insulated tip is:

The most effective flow arrangement in a heat exchanger is:

In a counter-flow heat exchanger, hot fluid enters at 150 °C and leaves at 100 °C; cold fluid enters at 50 °C and leaves at 100 °C. The LMTD is:

For a condenser (one fluid at constant temperature), the effectiveness is:

A cooling tower is an example of a:

NTU of a heat exchanger is defined as:

Which of the following is a renewable energy resource?

The coal with the highest carbon content and calorific value is:

Proximate analysis of coal determines:

The calorific value of gaseous fuels is measured using a:

The main constituent of natural gas is:

Solar photovoltaic cells convert sunlight into electricity using:

The main combustible gas in biogas is:

If wind speed doubles, the power available in the wind becomes:

The maximum theoretical power coefficient of a wind turbine (Betz limit) is:

A micro-hydro plant has Q = 0.1 m³/s, H = 50 m and overall efficiency 0.6. Its power output is about:

In a nuclear reactor, the function of the moderator is to:

A fuel cell produces electricity by:

The mass of oxygen required for complete combustion of 1 kg of carbon is:

The mass of oxygen required for complete combustion of 1 kg of hydrogen is:

Air contains approximately what percentage of oxygen by mass?

The stoichiometric air-fuel ratio for petrol is about:

The three Ts necessary for good combustion are:

In an Orsat apparatus, CO2 is absorbed by:

The period in a CI engine between the start of injection and the start of combustion is called:

Extinguishing a fire by shutting off the fuel supply is called:

Carbon monoxide is dangerous mainly because it:

Oxides of nitrogen are formed in engines mainly due to:

The main pollutants from diesel engines are:

A three-way catalytic converter operates efficiently only when the air-fuel mixture is:

Which hydrocarbon family has the best anti-knock quality for SI engines?

Which hydrocarbons make the best diesel (CI) fuels?

The octane number of iso-octane is:

The reference fuels for cetane number are:

Compared with MON, the RON of a petrol is usually:

The refining process that converts naphtha into aromatics to raise octane number is:

Amyl nitrate is added to diesel fuel to:

Before starting a diesel engine after the fuel system is opened, it is necessary to:

The lubrication system used in most automobile engines is:

In the oil grade SAE 20W-50, 'W' indicates:

In the API classification, engine oils for petrol (spark-ignition) engines carry the letter:

An engine has bsfc = 0.3 kg/kWh using fuel of CV 40,000 kJ/kg. Its brake thermal efficiency is:

Which of the following is a secondary air pollutant?

Photochemical smog is mainly formed by the reaction of:

The most suitable device for removing fine fly-ash particles from power-plant flue gas with over 99% efficiency is:

SO2 in flue gases is commonly removed by:

A temperature inversion in the atmosphere results in:

The plume behaviour that brings pollutants down to ground level, considered the worst condition, is:

BOD is conventionally measured over:

Excessive nitrogen and phosphorus in lakes lead to:

If two equal noise sources of 80 dB operate together, the combined level is about:

The most preferred option in the solid waste management hierarchy is:

The international treaty that phased out ozone-depleting substances is the:

The Paris Agreement (2015) aims to limit global temperature rise to:

In Nepal, environmental assessment requirements (BES, IEE, EIA) are laid down by the: