HEAT EXCHANGER

Abstract

A heat exchanger system comprises a heat exchanger; and one or more sensor(s) for measuring characteristics of a fluid flow field across a cross-section of a flow path in the heat exchanger. Each of the one or more sensor(s) comprises multiple conductivity sensing elements distributed across multiple locations in an array extending over the cross-section of the flow path for obtaining measurements of the fluid flow field at the multiple locations.

Claims

1. A heat exchanger system comprising: a heat exchanger; and one or more sensor(s) for measuring characteristics of a fluid flow field across a cross-section of a flow path in the heat exchanger; wherein each of the one or more sensor(s) comprises multiple conductivity sensing elements distributed across multiple locations in an array extending over the cross-section of the flow path for obtaining measurements of the fluid flow field at the multiple locations.

2. A heat exchanger system as claimed in claim 1, including one or more sensor(s) at one or more of a cross-section of a flow path at an inlet and/or an outlet of the heat exchanger, within a manifold or flow distributor such as a tank, at an entrance and/or an exit from a heat exchanger core of the heat exchanger, part-way through a heat exchanger core of the heat exchanger and/or at any other selected location in the heat exchanger.

3. A heat exchanger system as claimed in claim 2, further comprising: two or more sensors at the heat exchanger core for measuring the distribution of fluid density, flow rate or temperature in a fluid flow field of two or more cross-sections at the core, wherein the sensors are located at two or more of an entrance to the core, and an exit from the core, or within the core and part-way through the core.

4. A heat exchanger system as claimed in claim 1, wherein each of the one or more sensor(s) comprise multiple conductivity sensing elements having electrode pairs with a space in between the electrodes, wherein the fluid in the fluid flow path can fill the space when the heat exchanger is in use; and wherein each electrode pair is provided by a pair of wires that cross over with a space between the wires.

5. A heat exchanger system as claimed in claim 1, wherein the multiple electrode pairs are provided by two spaced apart layers of wires, wherein each layer comprises a row of wires with the wires being arranged so that wires in a first of the two layers cross over the wires in a second of the two layers, for example forming a grid type pattern.

6. A heat exchanger system as claimed in claim 5, wherein the multiple intersections of the wires in the two layers form the multiple sensing elements, and wherein each layer the row of wires comprises parallel straight wires.

7. A heat exchanger system as claimed in claim 1, wherein: the distance between the layers is smaller than the spacing between the sensing elements; and wherein the distance between the layers is 5 mm or below, optionally 3 mm or below; and/or the spacing between the sensing elements is in the range 1 mm to 10 mm.

8. A heat exchanger system as claimed in claim 1, further comprising: a data processing device for recording or analysing the measurements from the sensor, wherein the data processing device includes a data transmission circuit for wireless transmission of data from the sensor to other parts of the data processing device and/or to an external data processing system.

9. A heat exchanger system as claimed in claim 1, further comprising: a data processing device for recording or analysing the measurements from the sensor, wherein the data processing device includes circuitry embedded in the heat exchanger.

10. A heat exchanger system as claimed in claim 1, further comprising: a data processing device for recording and/or analysing the measurements from the sensor, wherein the data processing device is configured to analyse the measurements from the sensor in order to determine one or more types of information concerning the fluid flow field and to map a distribution of one or more of these types of information, such as a two dimensional mapping over the area of the sensor and/or the data processing device is configured to record data from the sensor over a period of time and make a comparison between multiple sets of data obtained at different times in order to identify changes occurring over time.

11. A heat exchanger system as claimed in claim 1, wherein the fluid to be measured is a multi-phase fluid including a gas as well as liquid and/or a mixture of liquids, and wherein the sensor is used to measure the distribution of the constituents of the multi-phase fluid.

12. A heat exchanger system as claimed claim 1, in combination with an aircraft.

13. A method of manufacturing a heat exchanger system comprising: installing a sensor within a heat exchanger, the sensor for measuring characteristics of a fluid flow field across a cross-section of a flow path in the heat exchanger; wherein the sensor comprises multiple conductivity sensing elements distributed across multiple locations in an array extending over the cross-section of the flow path for obtaining measurements of the fluid flow field at the multiple locations.

14. A method as claimed in claim 13, wherein the method includes forming at least a portion of the heat exchanger by additive manufacturing and forming the sensing elements using the same additive manufacturing process.

15. A method of analysing characteristics of a fluid flow field across a cross-section of a flow path in a heat exchanger; the method comprising: using a sensor comprising multiple conductivity sensing elements distributed across multiple locations in an array extending over the cross-section of the flow path to obtain measurements of the fluid flow field at the multiple locations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] A preferred embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

[0026] FIG. 1 shows an example cross-flow heat exchanger;

[0027] FIG. 2 is a cross-section through a heat exchanger showing flow distribution at the heat exchanger core; and

[0028] FIG. 3 shows a sensor or obtaining measurements of a fluid flow field in the heat exchanger.

DETAILED DESCRIPTION

[0029] An example heat exchanger 100 is shown in FIG. 1. The heat exchanger 100 is formed by an additive layer manufacturing technique. It receives heated liquid 120 and is arranged to exchange heat between the heated liquid 120 and a cool fluid 140 that enters the heat exchanger 100 from a perpendicular direction to the heated fluid 120. The cool fluid 140 exits the heat exchanger 100 in the direction 150, having absorbed heat from the heated liquid 120. The heated liquid 120 leaves the heat exchanger 100 in the direction 160 having transferred heat to the cool fluid 140.

[0030] FIG. 2 shows the distribution of liquid fluid flow through the heat exchanger 100 of FIG. 1. The heated fluid 120 enters the heat exchanger 100 into a distributor tank 104, where the flow spreads and disperses across the heat exchanger core 102. After flowing through the heat exchanger core 102 the cooled liquid exits via a collector tank and flows out via an outlet in the direction 160. It can be useful to monitor the flow distribution in order to provide both real-time monitoring of the fluid flow field and health/condition monitoring data for the heat exchanger system and optionally for a broader thermal management system. In order to measure the fluid flow field the heat exchanger 100 can be provided with a sensor 90 as shown in FIG. 3.

[0031] This sensor 90 can be positioned at any cross-section of the fluid flow path through the heat exchanger 100, for example at an inlet and/or an outlet of the heat exchanger, within a manifold or flow distributor such as the distributor tank 104, at an entrance and/or an exit from the heat exchanger core 102, part-way through the heat exchanger core 102 and so on. Multiple sensors 90 at different positions can be present in order to allow for measurement of the fluid flow field across multiple cross-sections, and hence enable further information to be derived about operation of the heat exchanger 100. The heat exchanger 100 may have a modular core 102 to permit a sensor 90 to be positioned within the core 102, i.e. where the fluid flow path measured by the sensor is part-way through the core 102.

[0032] The sensor 90 has a layered construction as shown in FIG. 3 with a first electrode layer 106 having a first set of parallel wires 108 that cross to form intersections 110 with a second electrode layer 112 having a second set of parallel wires 114. The two layers 106, 112 are spaced apart by a small distance, for example a few mm, and they have electrical connections so that the wires of one layer acts as emitter electrodes while the wires of the other layer act as a receiver electrodes. The intersections 110 of the two sets of wires 108, 114 form multiple electrode pairs that provide multiple conductivity sensing elements 110 spaced apart over the fluid flow field. Each of the layers 106, 112 is provided with a multiplexer circuit 124 for transmitting and receiving voltage pulses through the individual wires as described below. The fluid flowing through the heat exchanger can fill the space between the electrode pairs and by measuring the conductivity of the fluid between the electrode pairs then characteristics of the fluid can be determined, such as density, temperature, flow speed, fluid phase/phase mixture or gas fractions. The two layers 106, 112 of parallel wires 108, 114, form a grid with multiple evenly spaced conductivity sensing elements 110 that can measure the fluid flow field across the whole cross-section of the flow area. The resolution can be relatively high, with spacing between the wires of 2 mm easily achievable, with suitably narrow gauge wire.

[0033] One of the two layers 106, 112 of wires 108, 114 serves as a transmitter, while the other layer of wires serves as a receiver. Each wire in the transmitter plane is periodically activated by the appropriate multiplexer circuit 124 by a short voltage pulse. During the activation of individual wires as a transmitter then all other wires are kept at zero potential to avoid a risk of interference in the measurements. The electrical current passed to the receiver wire will be dependent upon the local instantaneous conductivity at each crossing point 110 of the transmitter and receiver wires 108, 114. This electrical current is transformed into a voltage using operational amplifiers and sampled by sample/hold circuits. The signal can be converted from analogue to digital before being recorded by a data processing circuit (not shown) connected to the sensor 90.

[0034] The data processing circuit records and analyses the data from the sensor 90 (and from multiple sensors 90 in some examples). The data processing circuit can obtain data at a high sampling rate and store it for later analysis or transmit it elsewhere, as desired. The data from the sensor 90 can be used for various purposes as discussed above.

[0035] It will be appreciated that the sensor 90 of FIG. 3 could equally well be used with other heat exchangers, obtaining the same advantages. The use of conductivity measurements provides best results when the fluid includes a liquid or mix of liquids as the fluid, or as a part of the fluid (for example in a two phase mixture), and so typically the fluid will be a liquid. The sensor 90 is particularly well-suited to use with aerospace heat exchangers and thus may advantageously be used in that context.