Ans: b. Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Ans: d. 21. Sensible heat is the heat required to (a) change vapour into liquid (b) change liquid into vapour (c) increase the temperature of a liquid of vapour (d) convert water into steam and superheat it (e) convert saturated steam into dry steam. 1. Learn how your comment data is processed. Thermal conductivity of water at 20°C is of the order of, 21. Except for water, aqueous solutions, and multihydroxy molecules, the thermal conductivity of most liquids decreases with temperature. Ans: e, 27. Metals are good conductors of heat because (a) their atoms collide frequently (b) their atoms-are relatively far apart (c) they contain free electrons (d) they have high density (e) all of the above. Ans: b, 12. Ans: b, 10. Ans: d, 22. Which of the following has least value of conductivity (a) glass (b) water (c) plastic (d) rubber (e) air. Ans: d. 20. Sensible heat is the heat required to. Ans: d, 13. ⇒ Thermal conductivity of water in general with rise in temperature increases decreases remains constant may increase or decrease depending on temperature ⇒ The wet bulb temperature at 100% relative humidity is _____ dry bulb temperature. Temperature of steam at around 540°C can be measured by (a) thermometer   (b) radiation pyrometer (c) thermistor       (d) thermocouple (e) thermopile. The amount of heat flow through a body by conduction is (a) directly proportional to the surface area of the body (b) directly proportional to the temperature difference on the two faces of the body (c) dependent upon the material of the body (d) inversely proportional to the thickness of the body (e) all of the above. Introduction to Seals : Ans: a, 16. In liquids, as we have seen earlier, thermal conductivity depends predominantly on molecular diffusion effect. Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application. Thermal conductivity is the property of a particular substance and shows the ease by which the process takes place. Which of the following is the case of heat transfer by radiation (a) blast furnace (b) heating of building (c) cooling of parts in furnace (d) heat received by a person from fireplace (e) all of the above. Thus, the thermal conductivity of a gas increases with increase in temperature. (b) change liquid into vapour. (c) … Related Questions on Heat and Mass Transfer All radiations in a black body are Ans: e, 17. Pick up the wrong case. Thermal conductivity of water at 20°C is of the order of (a) 0.1 (b) 0.23 (c) 0.42 (d) 0.51 (e) 0.64. Thermal conductivity of water in general with rise in temperature, 20. When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by, 7. How to calculate the temperature rise in a sealed enclosure. The amount of heat flow through a body by conduction is, (a) directly proportional to the surface area of the body, (b) directly proportional to the temperature difference on the two faces of the body, (c) dependent upon the material of the body, (d) inversely proportional to the thickness of the body, 29. When heat is Transferred by molecular collision, it is referred to as heat transfer by (a) conduction       (b) convection (c) radiation (d) scattering (e) convection and radiation. and Ans. Thermal conductivity of water at 20°C is of the order of (a) 0.1 (b) 0.23 (c) 0.42 (d) 0.51 (e) 0.64. engine       (b) air preheaters (c) heating of building in winter (d) all of the above (e) none of the above. ⇒ Thermal conductivity of water in general with rise in temperature increases decreases remains constant may increase or decrease depending on temperature ⇒ The wet bulb temperature at 100% relative humidity is _____ dry bulb temperature. Unit of thermal conductivity in M.K.S. Higher the thermal conductivity more easily will be the heat conduction through the substance. 19. Thermal conductivity of air with rise in temperature (a) increases (b) decreases (c) remains constant (d) may increase or decrease depending on temperature (e) none of the above. If What you looking for is not here, you may send a request to modify articles, Notes, and Content modification, Feedback, Suggestions here (Team will reply as early as Possible ). Ans: b, 11. Initially, when the rate of heat transfer is high, the hot water has a temperature of 70°C and the cold water has a temperature of 5°C. link to Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application, link to Slotter Machine - Types, Parts, Operations, Diagram, Specification. In order to calculate the surface temperature, T 3, as a result of ID scale formation, ho is first calculated from equation 4 given the design parameters of Uo, r3, n, hs, and for the clean tube condition. The time constant of a thermocouple is (a) the   time   taken   to   attain   the   final temperature to be measured (b) the time taken to attain 50% of the value of initial temperature difference (c) the time taken to attain 63.2% of the value of initial temperature difference (d) determined by the time taken to reach 100°C from 0°C (e) none of the above. 9. Ans: a, 25. Your email address will not be published. There are several ways to measure thermal conductivity; each is suitable for a limited range of materials. Water - temperature directly proportional to "K" Thank you For Visiting. Often times electrical or electronic components are housed in sealed enclosures to prevent the ingress of water, dust or other contaminants. Ans: c, 15. Heat is closely related with (a) liquids (b) energy (c) temperature     (d) entropy (e) enthalpy. 19. Ans: d, 20. Since in question already condition of temperature is mentioned (Rise - Increased) Ans: d, 21. same as lower than higher than none of these. Introduction to Slotting Machine : The concept of overall coefficient of heat transfer is used in heat transfer problems of (a) conduction       (b) convection (c) radiation (d) all the three combined (e) conduction and convection. In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by, 28. The concept of overall coefficient of heat transfer is used in heat transfer problems of, 27. The two containers have a 65°C difference in temperature. Read more about this portal or Sachin Thorat click on below button! Ans: d, 18. Required fields are marked *. Thermal conductivity of water at 20°C is of the order of (a) 0.1 (b) 0.23 (c) 0.42 (d) 0.51 (e) 0.64. The slotter or slotting machine is also a reciprocating type of machine tool similar to a shaper. Which of the following is a case of steady state heat transfer (a) I.C. Thermal conductivity of water in general with rise in temperature (a) increases (b) decreases (c) remains constant (d) may increase or decrease depending on temperature (e) none of the above. Ans: c, 9. The thermal conductivity of a material is a measure of its ability to conduct heat. Which of the following is expected to have highest thermal conductivity (a) steam (b) solid ice (c) melting ice       (d) water (e) boiling water. Same happens when we heat water, as the temperature increases the water expands making atoms move more freely enabling to transfer heat at increased speed (the resistance between atom decreaed) so the thermal conductivity increase with increase temprature. Values of k L for most common organic liquids range between 250 and 400 μcal/cm.s.°C at temperatures below the normal boiling point. From 0 K it is start from zero value and in a particular temperature it reach a maximum peak. Heat flows in the opposite direction to the temperature gradient. Cork is a good insulator because it has (a) free electrons (b) atoms colliding frequency (c) low density     (d) porous body (e) all of the above. It may be considered as a vertical shaper. Ans: d, 19. thermal conductivity of scale, W/M-C (Btu/ hr-ft-F). D. May increase or decrease depending upon temperature, "C" is correct Save my name and email in this browser for the next time I comment. The time constant of a thermocouple is, (a) the   time   taken   to   attain   the   final temperature to be measured, (b) the time taken to attain 50% of the value of initial temperature difference, (c) the time taken to attain 63.2% of the value of initial temperature difference, (d) determined by the time taken to reach 100°C from 0°C, 24.