84851. In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.
84852. Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since
84853. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
84854. The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.
84855. The by-pass factor of a cooling coil decreases with
84856. Dehydration is the process of removing water vapour from the surrounding air.
84857. The cooling of air, without any change in its specific humidity, is known as sensible cooling.
84858. The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.
84859. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
84860. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called
84861. The expansion valve in a refrigerator controls the flow of refrigerant.
84862. Upto the critical radius of insulation,
84863. The relative humidity lines on a psychrometric chart are
84864. A vapour absorption refrigeration system
84865. The rato of energy transferred by convection to that by conduction is called
84866. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg)
84867. Wet bulb temperature indicates the moisture content in air.
84868. A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is
84869. The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates wet bulb temperature.
84870. The heat is transferred by conduction, convection and radiation in
84871. A thermostatic expansion valve in a refrigeration system
84872. The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible.
84873. The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called
84874. For unsaturated air, the dew point temperature is __________ wet bulb temperature.
84875. During dehumidification process, __________ remains constant.
84876. Pressure of water vapour is given by
84877. Emissivity of a body will be equal to its absorptivity at all temperatures.
84878. R-12 is generally preferred over R-22 in deep freezers since
84879. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called
84880. During sub-cooling, sensible heat from a liquid refrigerant is removed.
84881. The expression is used for calculating relative humidity.
84882. If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called
84883. Dry bulb temperature is the temperature of air recorded by a thermometer, when
84884. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
84885. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
84886. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The by-pass factor of the heating coil is
84887. An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by
84888. The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.
84889. The emissivity of a polished silver body is __________ as compared to black body.
84890. In a pressure enthalpy chart, the space between the saturated liquid line and saturated vapour line, represents sub-cooled liquid region.
84891. R-11 has the highest critical point temperature.
84892. The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called
84893. Air refrigerator works on
84894. The reciprocating refrigerant compressors are very suitable for
84895. The boiling point of carbon dioxide is
84896. The mass of water vapour present in __________ is called absolute humidity.
84897. The relative coefficient of performance is equal to
84898. The cooling system used for supersonic aircrafts and rockets is
84899. The desirable property of a refrigerant is
84900. The humidification process, on the psychrometric chart is shown by
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