Engineering, 03.03.2020 17:31 pmgpmgutube

It takes a resistance heater having 2 kW power to heat a room having 5 m X 5 m X 6 m size to heat from 0 to 33 oC at sea level. Calculate the amount of time needed for this heating to occur in min (Please take Patm=101 kPa, give your answer with three decimals, and do NOT enter units!!!).

Answers: 2

Show answers

Answers

Answer from: veronica25681

50 minutes

Explanation:

The energy needed to heat air inside the room is the electric energy dissipated by the resistance. It is known after using First Principle of Thermodynamics:

$Q_{in,air} = \dot W_{dis, heater} \cdot \Delta t$

$\rho_{air} \cdot V_{room} \cdot c_{p,air} \cdot \Delta T = \dot W_{dis,heater} \cdot \Delta t$

The needed time is:

$\Delta t =\frac{\rho_{air}\cdot V_{room}\cdot c_{p,air} \cdot\Delta T}{\dot W_{dis,heater}}$

Where $\rho_{air} = 1.20 \frac{kg}{m^{3}}$ and $c_{p,air} = 1.012 \frac{kJ}{kg \cdot ^{\circ} C}$ :

$\Delta t = 3005.640 s (50.094 min)$

Answer from: Quest

answer:

dsfdssdfdssfdsfd

explanation:

Answer from: Quest

Infrared sensor is most used sensor in wireless technology where remote controlling functions and detection of surrounding objects/ obstacles are involved. this post will discuss about what is infrared sensor, its working principle, how it works, types, applications, advantages and disadvantages. what is infrared sensor

ir sensor is a simple electronic device which emits and detects ir radiation in order to find out certain objects/obstacles in its range. some of its features are heat and motion sensing.

ir sensors use infrared radiation of wavelength between 0.75 to 1000µm which falls between visible and microwave regions of electromagnetic spectrum. ir region is not visible to human eyes. infrared spectrum is categorized into three regions based on its wavelength i.e. near infrared, mid infrared, far infrared.

wavelength regions of infrared spectrum

near ir – 0.75µm to 3 µm
mid ir – 3 µm to 6 µm
far ir – > 6 µm
1 introduction to infrared sensor

fig. 1 – introduction to infrared sensor

working principle of infrared sensor

infrared sensors works on three fundamental physics laws:

planck’s radiation law: any object whose temperature is not equal to absolute zero (0 kelvin) emits radiation.
stephan boltzmann law: the total energy emitted at all wavelengths by a black body is related to the absolute temperature.
wein’s displacement law: objects of different temperature emit spectra that peak at different wavelengths that is inversely proportional to temperature.
key elements of infrared detection system

the key elements of infrared detection system are:

ir transmitter

ir transmitter acts as source for ir radiation. according to plank’s radiation law, every object is a source of ir radiation at temp t above 0 kelvin. in most cases black body radiators, tungsten lamps, silicon carbide, infrared lasers, leds of infrared wavelength are used as sources.

transmission medium

as the name suggests, transmission medium provides passage for the radiation to reach from ir transmitter to ir receiver. vacuum, atmosphere and optical fibers are used as medium.

ir receiver

generally ir receivers are photo diode and photo transistors. they are capable of detecting infrared radiation. hence ir receiver is also called as ir detector. variety of receivers are available based on wavelength, voltage and package.

ir transmitter and receivers are selected with matching parameters. some of deciding specifications of receivers are photosensitivity or responsivity, noise equivalent power and detectivity.

Another question on Engineering

Engineering, 03.07.2019 23:20

Two technicians are discussing the intake air temperature (iat) sensor. technician a says that the computer uses the iat sensor as a backup to the engine coolant temperature (ect) sensor. technician b says that the powertrain control module (pcm) will subtract the calculated amount of fuel if the air measures hot. who is correct

Answers: 3

Answer

Engineering, 04.07.2019 18:10

The thermal expansion or contraction of a given metal is a function of the f a)-density b)-initial temperature c)- temperature difference d)- linear coefficient of thermal expansion e)- final temperature f)- original length

Answers: 2

Answer

Engineering, 04.07.2019 18:10

Water at 55c flows across a flat plate whose surface temperature is held constant at 95c. if the temperature gradient at the plate's surface for a given value of x is 18 c/mm, find a) local heat transfer coefficient. b) heat flux

Answers: 3

Answer

Engineering, 04.07.2019 18:20

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]

Answers: 1

Answer

You know the right answer?

It takes a resistance heater having 2 kW power to heat a room having 5 m X 5 m X 6 m size to heat fr...

Questions