# US 2018/0324979 A1 · Apparatus and methods for characterizing a heat pipe and for controlling an operating parameter of at least one heat generating component coupled to the heat pipe

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- Number: US 2018/0324979 A1
- Document ID: US20180324979A1
- Status: Published application
- Kind: A1
- Application number: 15/585,509
- Filed: 2017-05-03
- Published: 2018-11-08
- Earliest claimed: 2017-05-03
- Assignees: Dell Products L.P.
- Applicants: Dell Products L.P.
- Inventors: Travis C. North; Andrew T. Sultenfuss
- Web page: https://patentgrep.com/patent/US20180324979A1

## CPC

- G05D 23/1917: {using digital means}
- G06F 1/20: Cooling means
- G06F 1/206: {comprising thermal management}
- F28F 2200/005: Testing heat pipes
- Y02D 10/00: Energy efficient computing, e.g. low power processors, power management or thermal management
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

Embodiments of apparatuses and methods are provided herein for characterizing a heat pipe, and for controlling an operating parameter of at least one heat generating component thermally coupled to the heat pipe based on a temperature difference measured across a first section and a second section of the heat pipe. For example, a characterization method is provided for determining at least one threshold value, which can be used to predict heat pipe dry-out within the heat pipe, and a thermal time constant (time lag) between the onset of heat pipe dry-out and a heat pipe dry-out limit. During subsequent system operation, the predetermined threshold value and thermal time constant may be used to extend the performance of the heat pipe to the edge of its cooling capacity.

## Claims

### Claim 1

A method for characterizing a heat pipe thermally coupled to a heat generating component of an information handling system, the method comprising:
obtaining temperature measurements from the heat pipe while supplying power to the heat generating component at a first power level for a first time period, and immediately thereafter increasing the supplied power to a second power level;
detecting an onset of heat pipe dry-out and a heat pipe dry-out limit from the temperature measurements; and
determining, from the temperature measurements, a temperature difference between a first temperature measured from the heat pipe at the onset of heat pipe dry-out and a second temperature measured from the heat pipe at the heat pipe dry-out limit.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein said detecting the onset of heat pipe dry-out comprises detecting the first temperature at which the temperature measurements obtained from the heat pipe transition from a steady state temperature to increasing at a substantially fixed rate, and wherein said detecting the heat pipe dry-out limit comprises detecting the second temperature at which the temperature measurements obtained from the heat pipe transition from increasing at the substantially fixed rate to increasing at a significantly greater rate than the substantially fixed rate.

### Claim 3 (depends on 1)

The method as recited in claim 1, further comprising determining, from the temperature measurements, a time duration between the onset of heat pipe dry-out and the heat pipe dry-out limit.

### Claim 4 (depends on 3)

The method as recited in claim 3, further comprising storing the temperature difference and the time duration.

### Claim 5 (depends on 4)

The method as recited in claim 4, wherein said obtaining temperature measurements from the heat pipe comprises obtaining temperature measurements from a first temperature sensor coupled to the heat pipe in the vicinity of the heat generating component and a second temperature sensor coupled to a condenser section of the heat pipe.

### Claim 6 (depends on 5)

The method as recited in claim 5, wherein a second heat generating component is thermally coupled to the heat pipe, and wherein the method further comprises:
obtaining additional temperature measurements from the second temperature sensor and a third temperature sensor, which is coupled to the heat pipe in the vicinity of the second heat generating component, wherein the additional temperature measurements are obtained while supplying power to the second heat generating component at the first power level for the first time period, and immediately thereafter increasing the supplied power to the second power level; and
detecting an onset of heat pipe dry-out and a heat pipe dry-out limit from the additional temperature measurements;
determining, from the additional temperature measurements, a second temperature difference between a third temperature measured from the heat pipe at the onset of heat pipe dry-out and a fourth temperature measured from the heat pipe at the heat pipe dry-out limit;
determining, from the additional temperature measurements, a second time duration between the onset heat pipe dry-out and the heat pipe dry-out limit; and
storing the second temperature difference and the second time duration.

### Claim 7

A method for controlling an operating parameter of a heat generating component of an information handling system, wherein the heat generating component is thermally coupled to a heat pipe, the method comprising:
determining an amount of power supplied to the heat generating component, wherein the heat generating component comprises a first power level limit and a second power level limit, which is greater than the first power level limit;
determining a temperature difference across a first section and a second section of the heat pipe corresponding to the heat generating component; and
decreasing a value of the operating parameter by a fixed amount, if the amount of power is greater than a maximum heat transportation limitation of the heat pipe and the temperature difference is greater than a first threshold value indicative of heat pipe dry-out.

### Claim 8 (depends on 7)

The method as recited in claim 7, wherein said operating parameter comprises at least one of a voltage, a current, a power, a frequency, a duty cycle, and a duration of time.

### Claim 9 (depends on 7)

The method as recited in claim 7, further comprising repeating the steps of determining an amount of power supplied to the heat generating component, determining a temperature difference, and decreasing a value of the operating parameter by the fixed amount until the amount of power is less than or equal to the maximum heat transportation limitation of the heat pipe and/or the temperature difference is less than or equal to the first threshold value.

### Claim 10 (depends on 7)

The method as recited in claim 7, further comprising setting the information handling system in a reduced performance mode, if the amount of power supplied to the heat generating component is less than or equal to the maximum heat transportation limitation of the heat pipe, but the temperature difference exceeds a second threshold value, which is less than the first threshold value.

### Claim 11 (depends on 10)

The method as recited in claim 10, wherein the step of setting the information handling system in a reduced performance mode comprises reducing the first power level limit and the second power level limit each by a predetermined amount.

### Claim 12 (depends on 7)

The method as recited in claim 7, further comprising:
determining an amount of power supplied to a second heat generating component thermally coupled to the first section of the heat pipe; and
determining a second temperature difference across the first section and the second section of the heat pipe corresponding to the second heat generating component.

### Claim 13 (depends on 12)

The method as recited in claim 12, further comprising:
determining a combined amount of power supplied to the heat generating component and the second heat generating component;
reducing the amount of power supplied to the heat generating component by the fixed amount, if the combined amount of power is greater than the maximum heat transportation limitation of the heat pipe and the temperature difference exceeds the first threshold value indicative of heat pipe dry-out; and
reducing the amount of power supplied to the second heat generating component by the fixed amount, if the combined amount of power is greater than the maximum heat transportation limitation of the heat pipe and the second temperature difference exceeds the first threshold value indicative of heat pipe dry-out.

### Claim 14

An apparatus for controlling an operating parameter of a heat generating component of an information handling system, wherein the heat generating component comprises a first power level limit and a second power level limit, which is greater than the first power level limit, and wherein the heat generating component is thermally coupled to a heat pipe, the apparatus comprising:
a first temperature sensor coupled to a first section of the heat pipe;
a second temperature sensor coupled to a second section of the heat pipe; and
a controller coupled to the first temperature sensor, the second temperature sensor and the heat generating component, wherein the controller is configured to:
determine an amount of power supplied to the heat generating component;
determine a temperature difference across the first and second sections of the heat pipe; and
decrease a value of the operating parameter by a fixed amount, if the amount of power is greater than a maximum heat transportation limitation of the heat pipe and the temperature difference is greater than a first threshold value indicative of heat pipe dry-out.

### Claim 15 (depends on 14)

The apparatus as recited in claim 14, wherein said operating parameter comprises at least one of a voltage, a current, a power, a frequency, a duty cycle, and a duration of time.

### Claim 16 (depends on 14)

The apparatus as recited in claim 14, wherein the controller is further configured to repeatedly determine an amount of power supplied to the heat generating component, determine a temperature difference, and decrease a value of the operating parameter by a fixed amount until the amount of power is less than or equal to the maximum heat transportation limitation of the heat pipe and/or the temperature difference is less than or equal to the first threshold value.

### Claim 17 (depends on 14)

The apparatus as recited in claim 14, wherein the controller is further configured to set the information handling system in a reduced performance mode, if the amount of power supplied to the heat generating component is less than or equal to the maximum heat transportation limitation of the heat pipe, but the temperature difference exceeds a second threshold value, which is less than the first threshold value.

### Claim 18 (depends on 17)

The apparatus as recited in claim 17, wherein the controller is configured to set the information handling system in the reduced performance mode by reducing the first power level limit and the second power level limit each by a predetermined amount.

### Claim 19 (depends on 14)

The apparatus as recited in claim 14, wherein the controller is further configured to:
determine an amount of power supplied to a second heat generating component thermally coupled to the first section of the heat pipe; and
determine a second temperature difference across the first section and the second section of the heat pipe corresponding to the second heat generating component.

### Claim 20 (depends on 19)

The apparatus as recited in claim 19, wherein the controller is further configured to:
determine a combined amount of power supplied to the heat generating component and to the second heat generating component;
reduce the amount of power supplied to the heat generating component by the fixed amount, if the combined amount of power is greater than the maximum heat transportation limitation of the heat pipe and the temperature difference exceeds the first threshold value indicative of heat pipe dry-out; and
reduce the amount of power supplied to the second heat generating component by the fixed amount, if the combined amount of power is greater than the maximum heat transportation limitation of the heat pipe and the second temperature difference exceeds the first threshold value indicative of heat pipe dry-out.