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Double Banked Fans

IP.com Disclosure Number: IPCOM000035414D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 89K

Publishing Venue

IBM

Related People

Bolton, IW: AUTHOR

Abstract

This article proposes the use of in-line counter rotating fans for cooling. These have been found to provide increased airflow at lower speed than two fans in parallel, thus increasing the reliability of equipment cooled and decreasing airflow noise.

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Double Banked Fans

This article proposes the use of in-line counter rotating fans for cooling. These have been found to provide increased airflow at lower speed than two fans in parallel, thus increasing the reliability of equipment cooled and decreasing airflow noise.

Tests were made in the drawer layout shown inset in both Figs. 1 and 2, with electronic equipment generating identical heat in spaces A, B, C, D and E.

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Fig. 1 shows the performance curves for two fans of a first type. If the noise level is limited to 5.2 Bels (sound), the flow rate would be 22 L/S (litres per second) and the fan speed is 1900 rpm.

Fig. 2 shows four fans assembled in a drawer; each pair consists of different fan types which rotate in opposite directions. Fig. 2 also shows the performance curves for such double-banked fans (both short throat fans). If the noise level is limited to 5.2 Bels, the flow rate would be 26.5 L/S and the fan speed 1300 rpm. Fan Reliability (assume service life L10 at 2,800 rpm X 30oC is 70K hrs.)is calculated as follows: L10 for fans AT 1900 rpm = 70K 28/19 = 85K hrs. L10 for fans AT 1300 rpm = 70K 28/13 = 103K hrs. However, the risk of a fan failure with 4 fans is still greater than with 2.

The advantage is a 20% increase in airflow and, therefore, greater overall reliability in equipment cooled without noise increase.

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