Effect Of Zoning

By evaluating the results of the analyses, maximum inequality was observed near the inlet region, where evaporator fans blow. So, it was thought that zoning the channel by dividing sub-sections, which were supplied by different fans, might provide a homogenous air distribution along the vehicle. And a new design strategy was applied. With this new design strategy, 2 air channels, which supply air to driver region and the passengers in the front 5 rows and passengers in last 8 rows, were designed. In this design front channel was supplied by inlets numbered 1 and 2, and rear channel was supplied by inlets numbered 3,4,5 and 6 with a main channel diameter of 150 mm and exit channel diameter of 50 mm. General design and detail of inlet region of zoned channel can be seen in Figure 4.38 and 4.39 respectively.

Figure 4.38. General design of the zoned channel

Figure 4.39. Detail of inlet region of the zoned channel

Area weighted average exit velocity and mass flow rate values obtained from the analyses of zoned channel are tabulated in Table 4.22 and graphed in Figure 4.40 and 4.41 respectively.

Table 4.22. Results obtained form analysis of 150/50 F2/R4 zoned channel

Exit

Figure 4.40. Graphic of area weighted average exit velocities of 150/50 F2/R4 zoned channel

Exit Mass Flow Rate

0,01 0,02 0,03 0,04

Exit 1 Exit 2 Exit 3 Exit 4 Exit 5 Exit 6 Exit 7 Exit 8 Exit 9 Exit 10

Exit 11

Exit 12

Exit 13

Exit 14 Exit Num ber

Mass Flow Rate (kg/s)

150/50 F2/R4

Figure 4.41. Graphic of mass flow rates of 150/50 F2/R4 zoned channel

As the results of the zoned channel was evaluated, it was determined that the area weighted average exit velocities of exits of front channel, which was supplied by 1 fan and having 6 exits, were lower than the exits of the rear channel supplied by 2 fans and having 8 exits. In order to balance the exit velocities and increase the velocities in the front channel, all properties were kept constant and exit channel diameter was taken as 35 mm for front channel and analyses were run again under the same conditions. General design and detail of inlet region of zoned channel can be seen in Figure 4.42 and 4.43 respectively.

Figure 4.42. General design of the zoned channel

Figure 4.43. Detail of inlet region of the zoned channel

Area weighted average exit velocity and mass flow rate values obtained from the analyses of zoned channel are tabulated in Table 4.23 and graphed in Figure 4.44 and 4.45 respectively.

Table 4.23. Results obtained form analysis of 150/35/50 F2/R4 zoned channel

Exit

Mass Flow Rate

Figure 4.45. Graphic of mass flow rates of 150/35/50 F2/R4 zoned channel

In this case while there is no change in the rear channel results, an extreme increase was observed in the exit velocities of the front channel. So that, while the average velocity of the exits of the previous front channel having 50mm diameter is about 8 m/s, average exit velocities of the new channel having 35 mm exit diameter is approximately 16 m/s.

In the case of examination of the mass flow rates, no change was observed in the rear channel. But in the front channel, because of the decrease in the exit channel diameter, an improvement was observed from the fluctuation point of view but still a lack of mass flow rate exists. Here it was understood that there would be no effect on lack of mass flow rate by altering exit diameter channel.

After that, in order to balance the amount of mass flow rate in the front channel, a new channel, which was supplied by 3 inlets for front and 3 inlets for rear with a main channel diameter of 150 mm and exit channel diameter of 50 mm, was designed. General design and detail of inlet region of the new channel can be seen in Figure 4.46 and 4.47 respectively.

Figure 4.46. General design of the new channel

Figure 4.47. Detail of inlet region of the new channel

Analyses were run with this geometry under the same conditions and area weighted average exit velocity and mass flow rate values obtained from the analyses of zoned channel are tabulated in Table 4.24 and graphed in Figure 4.48 and 4.49 respectively.

Table 4.24. Results obtained form analysis of 150/50 F3/R3 zoned channel

Exit

Area Weighted Average Exit Velocitiy

Area Weighted Average Exit Velocity (m/s)

150/35/50 F3/R3

Figure 4.48. Graphic of area weighted average exit velocities of 150/50 F3/R3 zoned channel

Figure 4.49. Graphic of mass flow rates of 150/50 F3/R3 zoned channel

An increase in the mass flow rate of the front channel by adding an inlet and some decrease in the mass flow rate of rear channel by canceling an inlet were observed at the results of the channel 150/50 F3/R3.

Comparison of the results of the first channel having 150 mm main and 50mm exit channel diameter without zoning, and with zoning by 3 inlets for front and 3 inlets for rear presented in Figure 4.50.

Mass Flow Rate

Figure 4.50. Comparison graphic of the effect of zoning

As can be observed from the graphic, zoning has a positive effect on fluctuations of mass flow rates of the exits located at the ends of the channels, however it cannot solve the problems on the inlet region with a 17% of overall standard deviation.

A general evaluation on zoning can be explained as follows;

Changing the location of the A/C rooftop unit, which is approximately 200 kg (Spheros, 2012), has a great effect on load distribution of the axles, roof structure and general strength of vehicle body. So chancing location of the A/C rooftop unit is not a simply applicable operation. While most of the heavy components like engine, transmission, radiator, exhaust etc were located to the rear of the engine, in order to balance weight distribution, A/C roof top unit was located to near of front portion of the vehicle. On the other hand, because of homogenous distance between the seats, exits were located homogeneously along the vehicle. So, the number of the exits to

be supplied by each of the fans cannot be equalized, (6 exits in the front channel, and 8 exits in the rear channel). As a result, chancing the location of the A/C rooftop unit is not a suitable solution for this situation.

Instead of chancing the location of A/C rooftop unit, chancing the locations of evaporator fans inside the A/C unit can be considered. But in this case, it was realized that the A/C unit is a standard product in the market. The manufacturer of A/C unit cannot accept chancing the properties of the product from customer to customer specially. So chancing the location of the fans inside the A/C unit is not a suitable solution for this situation again.

Finally, shifting the exit channels can be considered. But, locations of the exit channels were determined according to the seat layout, which is subjected to regulations and directives. So, since seat layout and consequently exit channel locations cannot be changed freely. Chancing the location of exit channels is not a suitable solution for us.

As a result of all these evaluations and investigations, it was decided not to employ a zoned channel.

Graphics of the resultant mass flow rates obtained from zoning applications are showed in Figure 4.51.

Figure 4.51. Comparison graphic of mass flow rates of all zoning applications