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# 121 297 Heat

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# Description

Examination number 1

5. Bring the wording of the first law of thermodynamics. Write analytical expression of this law for the basic thermodynamic processes

16. Describe Id - diagram of moist air. What are the simplest cases of its application?

Objective 5

In the process of air compression polytropic G = 65 x 103 kg / s, a single-stage reciprocating compressor in heat removal amount Q = 1,5, kJ / s. Upon compression of the initial absolute pressure of 0.1 MPa temperature increases from 15 0C to 95 0C t2 =. To determine the polytropic index of the compression process, the final pressure, the specific compression work and technical work on the compressed air, J / kg. What is the theoretical power required compressor drive, kW

Target 12

The installation for the preparation of distilled water for refilling the cooling system of locomotive diesel saturated steam having an absolute pressure P1 = 0.3 MPa and degree of dryness x = 0.95, condenses and oh-lazhdaetsya to a temperature t = 80 0C running water. How much water is required for preparing the distillate per day in an amount of 3 G = t / d, the temperature difference if the flow of water in the heat exchanger unit is Δtw = 20 K? Heat-exchange working bodies setting the environment ignored

Problem 22

What amount of air necessary to pass through the drying chamber to the material placed in it, take 1 ton of water? Outdoor air at barometric pressure = 745 mm Hg, with the temperature t1 = 10 0 C and relative humidity φ1 = 50% is heated in the heater to a temperature t2 = 66 0 C, and then air flows into the drying chamber and leaves it with a relative humidity φ2 = 90%. Solution of the pro-Id-illustrated in the chart

Task 25

Reciprocating internal combustion engine is ideal for the cycle with a supply of q = 850 kJ / kg heat at constant pressure. To determine the main parameters of the working body in the transition points in the cycle, its thermal efficiency and useful work, if the initial absolute pressure of 0.1 MPa, initial temperature of 80 0 C and the compression ratio ε = 13,5. The heat capacity of air is not considered independent of temperature. Tools body 1 kg of dry air. Show cycle pv and Ts - coordinates

Verification work number 2

2. Formulate the Fourier heat conduction law. Give an explanation to the concepts of "heat flux" and "temperature gradient"

20. What are the basic equations based thermal design of heat exchangers? What is the essence of design and verification of thermal calculations?

Target 10

Bare metal wire diameter d = 4 mm has a surface temperature Tw = 95 0C. Active electrical resistance wires r = 4 x 103 ohm / m. The coefficient of heat transfer from the surface of the wire to the surrounding air α = 15 W / m 2 K. The temperature of air ti = 22 0C. What will be the temperature of the surface of the wire t'st under insulation thickness δ = 3 mm with thermal conductivity coefficient λ = 0,2 W / mK at a constant current, and other things being equal? Determine also the maximum current in the insulated wire, if the initial temperature of the conductor considered the maximum allowable

Task 19

Tubing diameter d1 = 150 mm having a surface temperature t1 = 480 0C and the emissivity ε = 0,75, surrounded by cylindrical shield diameter d2 = 240 mm, both surfaces of which have the emissivity ε3 = 0,24.

Determine the heat loss by radiation to 1 running. m pipeline at ambient temperature t2 = 27 0C, taking its absorbance unity. What percentage of these losses will be greater under the same conditions for the pipeline without a screen?

Problem 29

The tubular air heater heats the air saturated water vapor pressure p = 0.1 MPa. The air inlet temperature t'v = 20 0C. Heat exchange surface area F = 1 m2. Determine the temperature of the air exiting the heater t''v if its consumption is G = 0,1 kg / s, and the heat transfer coefficient is k = 34 W / m2 K