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1.2.3 Method of calculation of system of heating and ventilatings of salon of the car, grounded on experimental data

The established temperature condition in salon in a stationary condition is defined by balance between the amount of warmth arriving from the outside (sunlight Q $) and from within (the drive, heating, a thermal emission from people QtI sitting in the car) and heat exchange through a surface of body QK And at the expense of warmth ablation by ventilating air QAL - the Thermal balance can be expressed a following equation (fig.

1.12):

Qh+QS'QK + QAL

Operation of system of ventilation and cooling is especially hampered in the summer in the conditions of direct operation of solar rays. The density of an arriving thermal stream makes in these conditions approximately

AND
1151,37 Vt/m also depend on quality of heat insulation of a body. At the area of an irradiated surface of salon of the car of the average size the thermal stream makes of 2,5 m approximately 2676,9 Vt which majority gets through windows. By application of the effective

Thermoisolation (first of all roofs), body and salon colourings in light (reflecting) colours, and also uses tonirovannyh glasses it is possible to diminish this thermal stream. Colour stipulates change of temperature in salon (if to compare bodies of white and black colour) in comparison with temperature of an environment depending on the sizes of the car on 8-15 %. Usual (netonirovannye), glasses pass light and thermal radiation almost easily, therefore conventional now the big windows in this respect are not the successful decision. At movement of the car air which is flowing round a body, has some cooling an effect but if additional refrigerators are not applied, temperature in salon constantly above environment temperature on 3 ° - 4°С basically for following reasons.

Fig. 1.12 Thermal balance at heating and ventilation (according to Franc) [52]

As a result of selection of warmth by the drive, transmission and system of issue of the completed gases, despite good isolation, there is a heating of air of salon. To it it is possible to add the warmth selected by people, being in the car which in a spacehold makes approximately 116,3 Vt. In the summer selection of the specified warmth (Qh) should compensate airing so that in salon

The temperature comprehensible to people was supported. So desired in the summer springback of warmth by a surface of body QK owing to too small overfall of temperatures in salon (t/) and outside (tij it is very insignificant. Therefore, if it is impossible to receive comprehensible temperature in salon by means of natural ventilation it is necessary to provide additional cooling of air arriving in salon by means of cooling system. By means of such system it is possible to regulate not only a temperature condition in salon, but also damp of air.

Some common data from area heating engineers are more low cited. Additional cooling of air of salon is necessary at environment temperature above 35°С and an intensive sunlight. In this case, air temperature in salon, in order to avoid danger of supercooling, should not be below temperature of an environment more than on 10 °, and the temperature of the cold air arriving from the heat exchanger, should not be more low 5°С. It is expedient to cool only a part of fresh air (approximately), other amount of arriving air it is necessary to use 30 % for osvezhenija air in salon then efficiency of use of air increases and constructive expenditures for the conditioner are diminished.

Certainly, car windows (with tonirovannymi glasses) should remain enclosed. Nevertheless, for air cooling the big power as it is necessary not only to cool air is consumed, but also to compensate its heat from a sunlight and internal "heating" of salon. According to Fiala for the average car this heat makes approximately 5233,5 Vt. The big advantage of additional cooling consists that with it relative damp of air in salon is diminished. It is diminished approximately by 35 % owing to cooling of a condensation moisture in the heat exchanger, that at a heat of an environment and high damp is perceived especially pleasantly.

In another way the requirements shown to system of heating and ventilation when it is necessary to raise air temperature in salon in the conditions of winter maintenance look. At projection of system of heating it is necessary to consider, that during airing, i.e. Ejection nagretogo air through provided for this hole and slots available in seals, there is a loss of warmth QAL is essentially diminishes EFFICIENCY of system of heating. The EFFICIENCY depends on many parametres, the part from which is defined more low.

QH = aGiXtj - t *) - amount of warmth (Vt), given system of heating;

QAL "aGiXU, - te) - warmth losses (Vt), at airing; Qfbw>" Qn - QAL - a Gl (to — toj) - effective productivity (Vt) systems of heating,

Where ta - temperature of air which is going out a heater; taj - temperature of air rejected from the car; tc - environment temperature; and - factor teplootdachi, and = 0,24—0,29 Вт/м2-К; Gl - amount of air circulating at enclosed windows (in winter conditions), m3/ch;

r - density of air of 1,2 kg/m (to accept depending on temperature and pressure of calculated process of heat exchange).

For the car of the average sizes at speed of 40 km/h and the working ventilator of heater GL = 210 m3/ch; ta = 64°С; tc =-20°S; Sr = 0,27; 1 ^ = 21°С.

Thus QH = 6646,545 Br, QAL = 3243,607 Vt; SFF = 3402,938 Vt. Then the EFFICIENCY of system of heating makes approximately 52 %.

Here loss of warmth Qk (radiation, a convection, a heat transfer), and also air heat in salon from the drive, system of issue of the completed gases and people being in salon is not considered. Warmth loss depends on air temperature difference in salon and outside

The car which in turn depends on amount of air arriving in salon, hence, from speed of movement, and also from quality of thermoisolation of salon (a roof, doors, bokoviny). Therefore the generalised formulas to reduce it is impossible. In the calculation reduced above warmth loss has made approximately 2093,4 Vt, that it is possible to use as approximate data. At calculation of system of heating it is necessary to consider only 60 % of the maximum air flow in the conditions of summer maintenance (all holes for air receipt are opened), therefore it is taken 3,5 m3/ch instead of 6,0 m3/ch (three completely open holes for air receipt). In quality, an example on fig. 1.13 the curve of dependence of productivity of the heat exchanger with a working surface of 0,035 m and depth of an element of 0,04 m from amount of arriving air is reduced. More exact data about demanded amount of warmth can be received only by means of measurements (at car trial). As approximate value of productivity of system of heating of the car of the average size Bart has suggested to accept 3954,2 - 5349,8 Vt.

Fig. 1.13 Dependence of power of a heater on expenditure of air for the middle class car (the heater area is equal 0,035м2, width of 0,04 m, tc = 255 To, ta = 335)

The heating system effectiveness can be augmented sharply by rise in temperature of air arriving from a heater, and also temperature of a cooling fluid of the drive by means of the thermostats adjusted on more heat of water (the "winter" thermostat), besides, by means of predusmatrivanija nonlinear regulation of amount of the arriving air, allowing to compensate increase in a high-speed pressure of air with growth of speed of the car. Change of temperature in salon depending on amount of air arriving from a usual heater, is displayed on fig. 1.14.

Fig. 1.14 Dependence of average temperature in salon tj from expenditure of air Gl at an ambient temperature,

Equal - 20 °

Speed of warming up of air in salon depends on how the head loop of system of heating (a cooling fluid of the drive) to working temperature (80-85°С) quickly gets warm, and it in turn depends on power of the drive. By regulation of the thermostat and additional heating of water in system of heating by means of the completed gases the warming up period can essentially be diminished.

The middle class car usually gets warm for 12-15 mines at the powered up third or fourth transmission (speed of the car of 40-60 km/h). On fig. 1.15 curve changes of temperature of air on an exit from a heater and air temperature in car salon are presented at a fixed ambient temperature (-20°S).

WITH

Fig. 1.15 Change of temperature of salon t, and temperatures on an exit from a heater t3: 1 - the third transmission, speed of 40 km/h; 2 fourth transmission.

Speed of 60 km/h

Considerably to diminish time of warming up of salon it is possible by means of the additional petrol heater which is powered up manually or automatically by means of a time element. Such heater can be used only for heating of air in car salon. Nsli a heater to power up in a head loop of system of cooling of the drive it can be applied and for predpuskovoju warming up.

The RUSSIAN l, STATE

LIBRARY

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A source: Matveev Denis Viktorovich. WORKING out of TECHNIQUE of CALCULATION of SYSTEM of HEATING And CAR VENTILATION. The thesis on competition of a scientific degree of a Cand.Tech.Sci. Izhevsk - 2006. 2006

More on topic 1.2.3 Method of calculation of system of heating and ventilatings of salon of the car, grounded on experimental data:

  1. 4.5 Experimental research of system of heating of car IZH-2126
  2. 1.2.2. A graphic method of calculation of air exchange in salon
  3. Matveev Denis Viktorovich. WORKING out of TECHNIQUE of CALCULATION of SYSTEM of HEATING And CAR VENTILATION. The thesis on competition of a scientific degree of a Cand.Tech.Sci. Izhevsk -, 2006 2006
  4. 4.3 Trials of system of heating and car IZH-2126 ventilation
  5. 2.2. The analysis of the physical processes occurring in system of heating and ventilation of the car
  6. 2. SIMULATION of AERODYNAMIC OPERATING MODES of SYSTEM of HEATING And CAR VENTILATION
  7. 3. NUMERICAL RESEARCH of the CURRENT of AIR In SYSTEM of VENTILATION And CAR HEATING
  8. 2.2 Mathematical model of the two-fuel combined system power supply of the drive of the car for expenditure calculation topliv
  9. 1.2.1 calculations of ventilation of salon Simplified an analytical method
  10. 4.1 Technique of experimental definition of air exchange in salon
  11. 3.1 Experimental research of a method of an estimation of a condition of the latent mastitis of cows on the basis of a clustering of data from sensing transducers
  12. the Flowchart of mathematical model of the two-fuel combined power supply system of the drive of the car for expenditure calculation topliv is presented in drawing 2.3. It has been developed on the basis of models/50, 66, 86,90/.
  13. Calculation of power efficiency of direct solar heating
  14. Calculation of power efficiency of devices of passive solar heating
  15. 3.2.2 Calculation of ecological efficiency of devices of passive solar heating
  16. Calculation of economic efficiency of devices of passive solar heating
  17. Algorithmic implementation of models of a data handling in system goniometricheskogo the control on baseline fazometricheskogo a method
  18. Calculation of a cost index of devices of passive solar heating
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