# US 10,767,940 B2 · Heat exchanger system and method of operation

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- Number: US 10,767,940 B2
- Document ID: US10767940B2
- Status: Granted
- Kind: B2
- Application number: 16/236,977
- Filed: 2018-12-31
- Published: 2019-05-09
- Granted: 2020-09-08
- Earliest claimed: 2016-06-24
- Assignees: Hamilton Sunstrand Corporation
- Applicants: Hamilton Sundstrand Corporation
- Inventors: Abbas A. Alahyari; Miad Yazdani; Craig R. Walker
- Web page: https://patentgrep.com/patent/US10767940B2

## CPC

- F28F 13/04: by preventing the formation of continuous films of condensate on heat-exchange surfaces, e.g. by promoting droplet formation {(F28F13/18 takes precedence)}
- F28F 13/10: by imparting a pulsating motion to the flow, e.g. by sonic vibration
- F28B 9/08: for collecting and removing condensate
- F28D 1/04: with tubular conduits {(F28D1/0246 takes precedence)}
- F28F 13/16: by applying an electrostatic field to the body of the heat-exchange medium
- F28F 17/00: Removing ice or water from heat-exchange apparatus
- F28F 17/005: {Means for draining condensates from heat exchangers, e.g. from evaporators (F28B9/08 takes precedence)}
- F28F 19/004: {by using protective electric currents, voltages, cathodes, anodes, electric short-circuits}
- F28F 19/02: by using coatings, e.g. vitreous or enamel coatings
- F28F 27/00: Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus (control arrangements in general G05)
- F25B 21/02: using Peltier effect; using Nernst-Ettinghausen effect
- F28F 2245/00: Coatings; Surface treatments
- F28F 2245/04: hydrophobic
- F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16)
- F28B: STEAM OR VAPOUR CONDENSERS (condensation of vapours B01D5/00; steam engine plants having condensers F01K; liquefaction of gases F25J; details of heat-exchange and heat-transfer arrangements of general application F28F)
- F28D: HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT (fluid heaters having heat generating means and heat transferring means F24H; furnaces F27; details of heat-exchange apparatus of general)
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS

## Abstract

A method of operating a heat exchanger is disclosed in which an electric field is applied to a hydrophobic surface having condensed water droplets thereon to reduce a contact angle between the individual droplet surfaces and the hydrophobic surface, and to increase droplet surface energy to a second surface energy level. The electric field is removed to increase the contact angle between the individual droplet surfaces and the hydrophobic surface, and to reduce droplet surface energy to a third surface energy level. The third surface energy level is greater than the first surface energy level and greater than a surface energy level for a free droplet. A portion of the droplet surface energy is converted to kinetic energy to detach droplets from the hydrophobic surface. The detached droplets are removed from the heat rejection side fluid flow path.

## Claims

### Claim 1

A heat exchanger system, comprising
a heat exchanger comprising a heat rejection side fluid flow path and a hydrophobic surface in thermal communication with a heat absorption side of the heat exchanger and in fluid communication with the heat rejection side flow path; and
a power source, electrodes, and a controller arranged to apply an electrical field to the hydrophobic surface,
wherein the controller is configured to apply the electric field to reduce a contact angle between condensate droplet surfaces and the hydrophobic surface and increase droplet surface energy to a second level greater than a first surface energy level for condensate droplets on the hydrophobic surface in the absence of an electric field, and to remove the electric field to increase the contact angle between the individual droplet surfaces and the hydrophobic surface and reduce droplet surface energy to a third surface energy level greater than the first surface energy level and greater than a surface energy level for a free droplet, and further wherein:
the controller is configured to apply an electrostatic charge to contaminants in the gas to promote capture of the contaminants by the droplets, or
the controller is configured to apply the electric field in response to a pressure differential between an inlet of the heat rejection side fluid flow path and an outlet of the heat rejection side fluid flow path, or
the controller is configured to apply the electric field in response to a temperature differential between a temperature of the hydrophobic surface and an ambient due point temperature higher than the hydrophobic surface temperature.

### Claim 2 (depends on 1)

The system of claim 1, wherein the controller is reconfigured to apply an electric field to impart an electrostatic charge to contaminants in the heat rejection side fluid flow path.

### Claim 3 (depends on 1)

The system of claim 1 wherein the controller is further configured to apply the electric field in response to: (i) a pressure differential between a heat rejection side fluid flow path inlet and outlet, (ii) a pressure differential between a heat rejection side fluid flow path inlet and outlet, or (iii) a differential between a temperature of the hydrophobic surface and an ambient dew point temperature higher than the hydrophobic surface temperature.

### Claim 4 (depends on 1)

The system of claim 1 wherein the controller is further configured to apply the electric field in a pulsed cycle pattern comprising alternating on and off periods wherein the duration of the off period is equal to or longer than the duration of the on period.

### Claim 5 (depends on 1)

The system of claim 1, wherein the hydrophobic surface is disposed on heat exchanger fins in thermal communication with the heat exchanger heat absorption side and in fluid communication with the heat rejection side fluid flow path.

### Claim 6 (depends on 5)

The system of claim 5, wherein the heat exchanger fins individually comprise a portion comprising a hydrophilic surface.

### Claim 7 (depends on 6)

The system of claim 6, wherein the hydrophobic surface comprises hydrophobic microstructural or nanostructural surface features.

### Claim 8 (depends on 1)

The system of claim 1, wherein the hydrophobic surface comprises a hydrophobic coating disposed on a heat exchanger surface in thermal communication with the heat exchanger heat absorption side and in fluid communication with the heat rejection side fluid flow path.

### Claim 9 (depends on 1)

The system of claim 1, wherein the heat exchanger hydrophobic surface comprises a heat exchanger structural feature formed from a hydrophobic polymer composition.