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The following data pertains to the junction of a thermocouple wire used to measure the temperature of the gas stream. Density = 8500 kg/m3, specific heat = 325 J/kg K, thermal conductivity = 40 W/m K and the heat transfer coefficient between the junction and gas = 215 W/m2 K. If thermocouple junction can be approximated as 1 mm diameter sphere, determine how long it will take for the thermocouple to read 99% of the initial temperature difference
A thermocouple junction in the form of 4 mm radius sphere is to be used to measure the temperature of a gas stream. The junction is initially at 35 degree Celsius and is placed in a gas stream which is at 300 degree Celsius. The thermocouple is removed from the hot gas stream after 10 seconds and kept in still air at 25 degree Celsius with convective coefficient 10 W/m2 K. Find out the time constant of the thermocouple. Assume the thermos-physical properties as given below h = 37.5 W/m2 K p = 7500 kg/m3 c = 400 J/kg K
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for junction diameter needed for the thermocouple to have thermal time constant of one second. Assume the thermos-physical properties as given below k = 20 W/ m K h = 350 W/m2 K c = 0.4 k J/kg K p = 8000 kg/m3
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for time required by the thermocouple to reach 197 degree Celsius temperature. Assume the thermos-physical properties as given below k = 20 W/ m K h = 350 W/m2 K c = 0.4 k J/kg K p = 8000 kg/m3
A J-type thermocouple has an output voltage Vθ = (13650 + 50 θx) μV, where θx is the junction temperature in Celsius (°C). The thermocouple is used with reference junction compensation, as shown in the figure. The Instrumentation amplifier used has a gain G = 20. If θRef is 1 °C, for an input θx of 100 °C, the output Vo of the instrumentation amplifier in millivolt is
A thermocouple-based temperature measurement system is shown in the adjoining figure. Relevant thermocouple emf data (in mV) is given below. The cold junction is kept at 0°C. The temperature is 30°C in the other parts of the system. The emf V is measured to be 26.74 mV. Th temperature of the hot liquid is Temp. emf of Chromel- Constantan emf of Copper- Constantan 10°C 0.591 0.391 20°C 1.192 0.789 30°C 1.801 1.196 370°C 26.549 19.027 380°C 27.345 19.638
“The response of a thermocouple is defined as the time required for the thermocouple to reach the surrounding temperature when it is exposed to it”.
The sensitivity of thermocouple is defined as the time required by thermocouple to reach how much percentage of its steady state values?
Emf developed by a thermocouple while measuring a temperature of 800°C is about 31 mV. The type of thermocouple used is
The temperature of a gas flowing in a long duct as measured by thermocouple (having an emissivity of 0.5) is 800 K. The internal wall surface of the duct is at a temperature of 500 K. The convective heat transfer coefficient between the gas and the tip of the thermocouple is 100 W-1 . K .-1 The actual gas temperature is actually . . . . . . . . K.