Engineering, 30.11.2019 03:31 ninaaforever

Liquid ammonia at −20°c is flowing through a 17-m-long section of a 5-mm-diameter copper tube at a rate of 0.09 kg/s. determine the pressure drop, the head loss, and the pumping power required to overcome the frictional losses in the tube. the density and dynamic viscosity of liquid ammonia at –20°c are rho

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Answer from: faithiemusic8821

Pressure drop = 971.52 KPa, Head Loss = 148.9 m, Pumping Power = 0.131 KW

Explanation:

T = -20 C, L = 17 m, Diameter = 5 x 10⁻³m, Mass (flow rate) = 0.09 kg/s

From table of properties of saturate ammonia at T = -20 C, ρ(density) = 665.1 kg/m³, μ(dynamic viscosity) = 2.36 x 10⁻⁴ kg/ms, Roughness of Copper tube)ε = 1.5 x 10⁻⁶

Calculate Area of cross sectional flow = (π/4) (D)² = (π/4) (5 x 10⁻³)² = 19.635 x 10⁻⁶ m²

Velocity of liquid = Mass (flow rate)/(ρ x Area cross sectional) = 0.09/665.1 x 19.635 x 10⁻⁶ = 6.89 m/s

Flow Rate (V) = Mass (flow rate)/ρ = 0.09/665.1 = 1.35 x 10⁻⁴ m/s

Reynold's Number (Re) = ρ x velocity x D/μ = 665.1 x 6.89 x 5 x 10⁻³/ 2.36 x 10⁻⁴ = 97087.7

The Re is greater than 4000, so the flow is said to be turbulent

For turbulent flow, use the Cole- brook equation

(1/√f) = -2.0㏒[{(ε/D)/3.7} + {2.51/(Re x √f)}]

(1/√f) = -2.0㏒[{(1.5 x 10⁻⁶/5 x 10⁻³)/3.7} + {2.51/(97087.7 x √f)}]

(1/√f) = -2.0㏒[{2.027 x 10⁻¹⁰ + {2.59 x 10⁻⁵/√f)}]

solve for f which is equal to 0.01810

Pressure Drop = f x (L/D) x (ρ x velocity²/2)

ΔP(l) = 0.01810x (17/5 x 10⁻³) x (665.1x 6.59²/2) = 971522.6 Pa = 971.52 KPa

Head Loss = ΔP(l)/ρ x g, where g is the acceleration due to gravity

H(l) = 971522.6/(665.1 x 9.81) = 148.9 m

Pumping Power Required = V x ΔP(l)

W(pump) = 1.35 x 10⁻⁴ x 9715522.6 = 131.16 W = 0.131 KW

Answer from: Quest

explanation:

an electrode is a metal whose surface serves as the location where oxidation-reduction equilibrium is established between the metal and what is in the solution.

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.

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Liquid ammonia at −20°c is flowing through a 17-m-long section of a 5-mm-diameter copper tube at a r...

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