The maximum current flowing in a cable depends essentially on the surface temperature of the cable...
The maximum current flowing in a cable depends essentially on the surface temperature of the cable that must not exceed the maximum temperature of the electrical insulation. A house thread AWG12 has a current rating of 25 A, when coated with thermoplastic so that the maximum temperature of the insulation is less than 60 ° C. To verify these data the following conditions are used: - Ac = 3.31 mm2 (section of the cable) - hconv = 4 W / m2K - hrad = 5 W / m2K. Rélec'= 5.31x10-3 ? / m. - T? = 30 ° C - Tsurr = 15 ° C - I = 25 A a) Calculate the surface temperature of the AWG12 cable without insulation; b) What is the emissivity of the cable? c) A thermoplastic insulator (k = 0.26 W / mK) of 1.45 mm thickness is added. Find the maximum temperature of the insulation. It is assumed that the coefficients "h" remain unchanged.
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The maximum current flowing in a cable depends essentially on the surface temperature of the
cable...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such that the convection heat transfer coefficient is h. To prevent cracking, it is known that the temperature gradient must not exceed 15 °C/mm at any point in the glass during the cooling process. The thermal conductivity of the glass is 1.4 W/mK and its surface emissivity is 0.75. The temperature of the air that is used for the cooling is 315 °C. Assume that...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boller to the turbine in a power plant. Safety and economic concerns make it practical to add a 200-mm layer of Insulation (k =0.1 W/mK) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity e =0.15. The air (with a convective coefficient h =5 W/m2K) and wail temperatures of the plant are...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
system, hot water at an average temperature of 80°C is flowing through a 15-m section of...
system, hot water at an average temperature of 80°C is flowing through a 15-m section of a cast In a heating iron pipe (k 50 W/m K) whose inner and outer diameters are 4 cm and 5 cm, respectively. The outer surface of the pipe, whose emissivity is 0.75, is exposed to the cold air at 10°C in the basement. with a heat transfer coefficient of 15 W/m2.K. The heat transfer coefficient at the inner surface of the pipe is...
Hot CO2 gas at a temperature T-1 = 250°C is flowing through a steel pipe (kı...
Hot CO2 gas at a temperature T-1 = 250°C is flowing through a steel pipe (kı = 70 W/(m.K)) whose inner and outer radiuses are 12 cm and 14 cm, respectively, in a cold environment at Tm2 = -10°C. As shown in the figure below, the steel pipe is insulated with 7.0 cm thick spray-foam insulation (k2 = 0.03 W/(m.K)) and 5.0 cm thick glassfiber insulation (k3 = 0.05 W/(m.K)). Consider the heat transfer coefficients of CO2 gas and the...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY. A hollow aluminum sphere, with...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY.
A hollow aluminum sphere, with an electrical heater in the center, is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively, and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250°C. In a particular test, a spherical shell of insulation is cast on the outer surface...
An electric car travels at a constant highway speed of 60 mph, requiring a battery current...
An electric car travels at a constant highway speed of 60 mph, requiring a battery current draw of 50 A. The cooling system operates such that the average convection coefficient, h, is 25 W/m2 K. The coolant average temperature is 23°C. Suddenly a cooling system malfunction results in a decrease of the convection coefficient to 5 W/m2K. The pack has a heat transfer surface area of 1.2m2 and a mass of 50 kg. The pack specific heat is 600J/kg K...
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 800°C...
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 800°C and 100°C, respectively. Determine the rate of heal transfer by radiation between the plates in Wim and the radiative heat transfer coefficient in W/m K ) 12 Write down the one-dimensional sent heal conduction equation for a plane wall with constant thermal conductivity and heat generation in its simplest form, and indicate what each variable represents 13 Write down the one-dimensional transient heat conduction...
pleas help me in this do any question you know using National Electrical Code 2011 Applied Electricity NEC...
pleas help me in this do any question you know using National
Electrical Code 2011
Applied Electricity NEC worksheet t hree Copper conductors with THHN insulation run in Electrical A branch-circuit Consther conductors. The conductor terminations are rated for a maximum ure in the area of this installation is not expected to exceed 30C size 8 AWG, the maximum ampacity of the conductors If the conductors for this circuit are permitted A 40 amperes. B. 50 amperes. to be used...
summarizr the followung info and write them in your own words and break them into different...
summarizr the followung info and write them in your own words and break them into different key points. 6.5 Metering Chamber: 6.5.1 The minimum size of the metering box is governed by the metering area required to obtain a representative test area for the specimen (see 7.2) and for maintenance of reasonable test accuracy. For example, for specimens incorporating air spaces or stud spaces, the metering area shall span an integral number of spaces (see 5.5). The depth of...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such that the convection heat transfer coefficient is h. To prevent cracking, it is known that the temperature gradient must not exceed 15 °C/mm at any point in the glass during the cooling process. The thermal conductivity of the glass is 1.4 W/mK and its surface emissivity is 0.75. The temperature of the air that is used for the cooling is 315 °C. Assume that...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boller to the turbine in a power plant. Safety and economic concerns make it practical to add a 200-mm layer of Insulation (k =0.1 W/mK) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity e =0.15. The air (with a convective coefficient h =5 W/m2K) and wail temperatures of the plant are...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
system, hot water at an average temperature of 80°C is flowing through a 15-m section of a cast In a heating iron pipe (k 50 W/m K) whose inner and outer diameters are 4 cm and 5 cm, respectively. The outer surface of the pipe, whose emissivity is 0.75, is exposed to the cold air at 10°C in the basement. with a heat transfer coefficient of 15 W/m2.K. The heat transfer coefficient at the inner surface of the pipe is...
Hot CO2 gas at a temperature T-1 = 250°C is flowing through a steel pipe (kı = 70 W/(m.K)) whose inner and outer radiuses are 12 cm and 14 cm, respectively, in a cold environment at Tm2 = -10°C. As shown in the figure below, the steel pipe is insulated with 7.0 cm thick spray-foam insulation (k2 = 0.03 W/(m.K)) and 5.0 cm thick glassfiber insulation (k3 = 0.05 W/(m.K)). Consider the heat transfer coefficients of CO2 gas and the...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY.
A hollow aluminum sphere, with an electrical heater in the center, is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively, and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250°C. In a particular test, a spherical shell of insulation is cast on the outer surface...
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 800°C and 100°C, respectively. Determine the rate of heal transfer by radiation between the plates in Wim and the radiative heat transfer coefficient in W/m K ) 12 Write down the one-dimensional sent heal conduction equation for a plane wall with constant thermal conductivity and heat generation in its simplest form, and indicate what each variable represents 13 Write down the one-dimensional transient heat conduction...
pleas help me in this do any question you know using National
Electrical Code 2011
Applied Electricity NEC worksheet t hree Copper conductors with THHN insulation run in Electrical A branch-circuit Consther conductors. The conductor terminations are rated for a maximum ure in the area of this installation is not expected to exceed 30C size 8 AWG, the maximum ampacity of the conductors If the conductors for this circuit are permitted A 40 amperes. B. 50 amperes. to be used...
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