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Hot air for a large-scale drying operation is to be produced by routing the air over a tube bank (unmixed), while products of combustion are routed through the tubes. The surface area of the cross-flow heat exchanger is A = 25 m2, and for the proposed operating conditions, the manufacturer specifies an overall heat transfer coefficient of V = 35 W/m2 · K. The air and the combustion gases may each be assumed to have a specific heat of cp = 1040 J/kg · K. Consider conditions for which combustion gases flowing at 1 kg/s enter the heat exchanger at 800 K, while air at 5 kg/s has an inlet temperature of 300 K.
(a) What are the air and gas outlet temperatures?
(b) After extended operation, deposits on the inner tube surfaces are expected to provide a fouling resistance of R'f = 0.004 m2 · K/W. Should operation be suspended in order to clean the tubes?
(c) The heat exchanger performance may be improved by increasing the surface area and/or the overall heat transfer coefficient. Explore the effect of such changes on the air outlet temperature for 500 < ua="">< 2500="" w/k.="">
An electric pencil sharpener is rated 240 mW, 6 V is connected to a 9-V battery and a series-dropping resistor Rx needed to power the sharpener. Calculate the value of the series-dropping resistor Rx needed to power the sharpener.
A sheet of plywood 1.39 cm thick is used to make a cabinet door 55.5 cm wide by 69.5 cm tall, with hinges mounted on the vertical edge. A small 181-g handle is mounted 45 cm from the lower hinge at the same height as that hinge.
The accompanying schematics each show two inductors with coupling but with different dot markings. For each of the two systems, determine the equivalent inductance of the system at terminals 1-1' by combining inductances.
A separately excited DC generator,when running at 1200 RPM, supplies 200A at 125V to a circuit ofconstant resistance. What will the current be when the speed is reduced to 1000 RPM if the field current remains unchanged
Determine the primary current when rated current in the 230 volt winding is at unity power factor and the rated current in the 575 volt winding is at .5 pf lagging. Neglect all leakage impedance drops and magnetizing current.
In a scanning electron microscope, an electron is accelerated by a static electrode biased with a 12 kV voltage relative to the electron source. Upon bombarding the sample the electron “kick out†photons with specific wavelength.
A 120V source is connected in parallel with four (4) resistors, all of which are in parallel. The resistors have the ratios 1 : 2 : 3 : 6 (for example 4Ω, 8Ω, 12Ω, 24Ω). The source delivers 288W to the parallel combination.
A full wave center-tapped transformer rectifier ina power supply provides an average dc output voltage of 14V onwhich a maximum ripple of ±0.5 volt is allowed. Diodeshave a 0.7 Volt drop when conducting. Assuming a resistive load of120 ohm
Given a 100-MHz clock signal, derive a circuit using D flip-flops to generate 50-MHz and 25-MHz clock signals. Draw a timing diagram for all three clock signals, assuming reasonable delays.
One of the firm's suppliers discounts prices for larger quantities. The first 1000 parts are $13 each. The next 2000 are $12 each. All parts in excess of 3000 cost $11 each. What are the average cost and marginal cost per part
Assuming the resistance versus temperature function to be linear, determine the expected resistance of the material at 0 degrees celcius( the freezing point of water) and at 100 degrees celcius (the boiling point of water)
What would be the band gap voltage needed for a material to fabricate an LED that can emit blue light - Design a system for measurements of snoring sounds in heavy snorers using a piezoelectric crystal.
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