Method and apparatus for fan control to achieve enhanced cooling

• US 5,102,040 A
• Filed: 03/28/1991
• Issued: 04/07/1992
• Est. Priority Date: 03/28/1991
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Harvey, William J.
• Primary Examiner(s): Tanner, Harry B.
• Assistant Examiner(s): SOLLECITO, JOHN M
• Application Number:
  US07/678,555
• Time in Patent Office: 376 Days
• Field of Search: 236/49.3, 236/94, 236/DIG. 9, 165/80.2, 165/80.3, 165/40, 165/11 R, 416/44, 417/22, 417/19, 417/32, 417/14, 417/292, 364/382, 364/383, 364/384, 364/385
• US Class Current: 236/49.3
• CPC Class Codes: F24F 11/0001 for ventilation F24F11/30 takes precedence
• CPC Class Codes: G05D 23/1931 to control the temperature of one space
• CPC Class Codes: Y10S 236/09 Fan control

Abstract

Enhanced cooling of electronic equipment (14) within an enclosure (10) is obtained by prescribing the relationship between the maximum allowable temperature difference ΔT_m between the exhaust and inlet air temperatures T_e and T_i versus the actual inlet temperature. Once a relationship between the maximum allowable temperature difference ΔT_m versus inlet temperature T_i has been established, then each fan (22) which draws air through the enclosure is controlled so that the fan'"'"'s speed is increased when the actual temperature ΔT exceeds the maximum allowable temperature difference ΔT_m by a predetermined tolerance factor. In this way, factors such as increased heat load in the enclosure (10), diminution of the air flow therethrough, as well as an increase in the inlet air temperature, are taken account of in the control of fan speed.

Claims

1. A method for controlling the speed of at least one fan which forces air through an enclosure to enhance the cooling of equipment within the enclosure, comprising the steps of:

(a) prescribing a relationship between the maximum allowable difference (Δ

T_m) between the temperature of air entering the enclosure (T_i) and the temperature of air exhausted from the enclosure (T_e) for a given value of T_i ;

(b) monitoring both T_i and T_e ;

(c) determining the difference between the actual value of Δ

T and the maximum allowable value of Δ

T_m corresponding to the actual value of T_i ; and

(d) increasing the speed of the fan when the actual value of Δ

T exceeds the maximum allowable value of Δ

T_m by more than a predetermined tolerance factor.

2. The method according to claim 1 wherein the steps of (b)-(d) are repeatedly executed at a rapid rate.

3. The method according to claim 1 including the steps of:

(a) prescribing a relationship between the fan speed and the maximum allowable temperature difference Δ

T_m ;

(b) monitoring the fan speed;

(c) determining the maximum allowable temperature difference Δ

T corresponding to the actual fan speed;

(d) comparing the maximum allowable temperature difference Δ

T_m corresponding to the actual fan speed to the actual temperature difference Δ

T and signaling an alarm condition if the maximum allowable Δ

T_m exceeds the actual Δ

T by more than a predetermined tolerance.

4. The method according to claim 3 wherein the steps of (b)-(d) are performed repeatedly at a high rate.

5. The method according to claim 3 including the steps of:

(a) detecting if the fan speed increases while the actual value of Δ

T remains substantially constant; and

, if so

(b) signaling a change in such fan speed.

6. A fan controller for controlling at least one fan drawing air through an enclosure containing at least one piece of heat-generating equipment therein to enhance the cooling of such equipment, comprising;

first temperature-sensing means for sensing the temperature (T_i) of air entering the inlet;

second temperature-sensing means for sensing the temperature (T_e) of air exiting the enclosure; and

processing means, programmed with a user-prescribed relationship between the maximum allowable temperature difference Δ

T_m between T_i and T_e versus T_i, for determining the difference between the actual temperature difference Δ

T and the maximum allowable temperature difference Δ

T_m corresponding to the current value of T_i and for increasing the speed of the fan when the difference between the actual and maximum allowable temperature differences exceeds a predetermined tolerance.

7. The apparatus according to claim 6 wherein said processing means is further programmed with a user-prescribed relationship between fan speed and the minimum achievable temperature difference and wherein said fan controller further includes means coupled to each fan for sensing the fan speed to enable the processor means to determine if the actual temperature difference Δ

T exceeds the minimum achievable temperature difference Δ

T_a, corresponding to the sensed speed, by a predetermined tolerance.

8. The apparatus according to claim 6 wherein each of the first and second temperature-sensing elements comprises a thermistor.