Process and device to detect a risk of water condensation on a surface being in contact with a wet air volume

• US 5,568,977 A
• Filed: 02/03/1994
• Issued: 10/29/1996
• Est. Priority Date: 02/24/1993
• Status: Expired due to Fees

• Current Assignee: Imra Europe S.A.S. (Aisin Corp.)
• Original Assignee: Imra Europe S.A.S. (Aisin Corp.)
• Inventors: Ancey, Pascal, Gschwind, Michel
• Primary Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US08/191,048
• Time in Patent Office: 999 Days
• Field of Search: 374/45, 374/54, 374/27, 374/28
• US Class Current: 374/45
• CPC Class Codes: G01N 25/68 by varying the temperature of a condensing surface

Abstract

A process is disclosed to detect a water condensation risk on a surface in contact with a wet air volume, which uses the steps of (a) placing a sensitive element on the surface, which initially takes a temperature corresponding to that of the surface, (b) by means of a heating device on this sensitive element, initiating a first heating phase until a temperature higher than the surface temperature is reached, (c) by means of a cooling device having the same thermal power as the heating device, initiating a cooling phase until a temperature lower than the surface temperature is provoked on the sensitive element, and (d) a comparison is made between the ratio of the first heating phase time to the temperature rise during heating and the ratio of cooling phase time to the temperature decrease during the cooling, a noticeable difference between these two ratios indicating a significant risk of condensation on the surface.

Claims

1. A process for detecting risk of water condensation on a surface in contact with a volume of wet air, comprising the steps of:

(a) placing a sensitive element on the surface causing the element to take on a temperature corresponding to the surface'"'"'s temperature,

(b) heating the sensitive element during a first heating phase with a heating device until a temperature higher than the surface'"'"'s temperature is reached,

(c) recording time duration and increase in temperature of the element during the first heating phase,

(d) cooling the sensitive element during a cooling phase with a cooling device having the same thermal capacity as the heating device until a temperature lower than the surface'"'"'s temperature is reached,

(e) recording time duration and decrease in temperature of the element during the cooling phase,

(f) comparing (1) the ratio of the first heating phase time duration to the temperature increase during the first heating phase to (2) the ratio of the cooling phase time duration to the temperature decrease during the cooling phase, wherein a difference between the ratios (1) and (2) corresponds to a risk of condensation on the surface.

2. The process as claimed in claim 1, wherein a predetermined temperature change for the first heating phase is used and the temperature of the element at the end of the cooling phase is set by subtracting the predetermined temperature change from the surface'"'"'s initial temperature, so that said comparing step (f) only needs to compare the time duration of the first heating phase to half the time duration of the cooling phase to determine the risk of condensation on the surface.

3. The process as claimed in claim 2, further comprising, after the recording step (e), heating the element during a second heating phase with the heating device until the temperature of the element returns to the surface'"'"'s temperature before the first heating phase and recording time duration of the second heating phase.

4. The process as claimed in claim 3, wherein said comparing step (f) only needs to compare the time duration of the first heating phase to a quarter of the total time duration of a cycle constituting the cooling phase time duration plus the second heating phase time duration to determine the risk of condensation on the surface.

5. The process as claimed in claim 3, wherein said comparing step (f) only needs to compare the time duration of the first heating phase to the time duration of the second heating phase to determine the risk of condensation on the surface.

6. The process as claimed in claim 3, wherein said comparing step (f) only needs to compare the time duration of the cycle constituting the cooling phase time duration plus the second heating phase time duration to a successive cycle constituting a second cooling phase time duration plus a third heating phase time duration to determine the risk of condensation on the surface.

7. The process as claimed in claim 1, wherein a Peltier effect module is used as the sensitive element, the heating device, and the cooling device;

and the temperature increase and temperature decrease are recorded by measuring the Seebeck component of voltage at the terminals of the Peltier effect module.

8. The process as claimed in claim 7, wherein the Seebeck component is obtained by eliminating a constant component representative of voltage due to internal resistance of the Peltier effect module at constant temperature.

9. The process as claimed in claim 7, wherein the Seebeck component is obtained by eliminating a variable component due to the internal resistance of the Peltier effect module at the average temperature of the module in the voltage at the terminals of the module.

10. A device for detecting risk of water condensation on a surface in contact with a volume of wet air comprising

(a) a sensitive element which, when contacted with the surface, takes on a temperature corresponding to the surface'"'"'s temperature,

(b) a heating device for heating the sensitive element during a first heating phase,

(c) means for recording time duration and increase in temperature of the element during the first heating phase,

(d) a cooling device for cooling the sensitive element during a cooling phase,

(e) means for recording time duration and decrease in temperature of the element during the cooling phase,

(f) a control unit for controlling the heating and cooling devices so that the element is first heated to a predetermined temperature above the surface'"'"'s temperature and then cooled to a temperature below the surface'"'"'s temperature, and

(g) means for comparing (1) the ratio of the first heating phase time duration to the temperature increase during the first heating phase to (2) the ratio of the cooling phase time duration to the temperature decrease during the cooling phase, wherein a difference between the ratios (1) and (2) corresponds to a risk of condensation on the surface.

11. The device as claimed in claim 10, wherein (a), (b) and (d) are a Peltier effect module powered by an electronic circuit that inverts current direction whenever the Seebeck component of voltage at the Peltier effect module terminals exceeds a predetermined value.