JP2014529054A - Operation method of gas-liquid heat exchanger - Google Patents

Abstract

A method of operating a gas-liquid heat exchanger in which heat is exchanged between liquid and air in at least a first passive heat exchange stage (2), comprising the following procedural steps: dew point of ambient air Calculate the temperature, determine whether the dew point temperature of the ambient air is higher than the temperature of the liquid, and if it is higher, operate the heat exchanger in an operating mode called pulsing according to the following steps: During which the first heat exchange stage (2) flows through, the liquid is prevented from flowing through the first stage, the temperature of the air is measured and monitored after flowing through the first heat exchange stage (2), The air temperature measured after leaving the first heat exchange stage (2) shows a first temperature rise, then stays at a substantially constant level for a certain period of time, then shows a second temperature rise, After the temperature rise is detected, and after the second temperature rise is detected, the liquid Heat exchange step (2) ends be blocked so as not to flow, and this process is repeated between the dew point temperature of the air is higher than the temperature of the liquid. [Selection] Figure 2

Description

  The present invention relates to a method for operating a gas-liquid heat exchanger.

  The method is suitable for operation of a gas-liquid heat exchanger having a passive heat exchange stage, in which the air passes through a first flow path extending vertically and the liquid passes through a second. Guided through the channels, the two channels are separated at this stage by thermally passive partitions. The term “thermally passive” means that the heat exchange takes place without performing work. These channels include a plurality of fins that are in good thermal connection with a thermally passive partition. The space between the fins in the air flow path is small compared to the surface area thereof, so that heat exchange is efficient.

  Especially when the relative humidity of air is high, such as on a hot day in summer, the dew point temperature of air may be higher than the temperature of the liquid. Thereby, the moisture contained in the air condenses on the fins as condensed water. Due to the generally small tolerance of the heat exchanger dimensions, it is difficult to form the fins so that the water generated in the fins is completely drained and discharged, especially when the air flow is guided vertically. As a result, water is visibly accumulated in the gaps between the fins, and air resistance is generated, so that the air cannot be efficiently cooled continuously.

  From US Pat. No. 6,057,049, a central heating system with at least one radiator that can also be used for cooling is known. In the cooling mode, the liquid circulating in the radiator is deprived of heat using a heat exchanger. The deprived heat is sent to the regenerator using a second heat exchanger. The two heat exchangers are part of a compressor driven heat pump. In order to prevent moisture from condensing with the radiator, the temperature and humidity around the radiator are measured to calculate the dew point of the air, and when the calculated dew point temperature approaches the temperature of the radiator, the cooling capacity is reduced.

  From patent document 2, a control method for an air conditioner is known. In this method, the temperature at which water condenses on the test element in the cooling mode is calculated, and the temperature of the coolant is adjusted to be higher than the condensation temperature. This is done, for example, by stopping the cooling mode.

  All solutions known from this prior art are aimed at preventing condensation from accumulating, which is achieved by reducing the cooling capacity or interrupting the cooling mode.

British Patent No. 2461365 European Patent No. 508766

  The object of the present invention is to solve the problems mentioned.

  The above problem is solved according to the invention by the features of claim 1. Advantageous embodiments are disclosed in the dependent claims.

  The present invention relates to the operation of a gas-liquid heat exchanger having a first flow path for air and a second flow path for liquid. The heat exchanger includes a first passive heat exchange stage in which the first flow path and the second flow path are separated by a thermally passive partition, and optionally a second flow path. An active heat exchange stage is included in which the air is cooled or heated in an active manner, i.e. by pumping heat from one side to the other. The thermally passive partition is made of a material that conducts heat well. In the second heat exchange stage, a suitable condensate drainage system is preferably installed. Each of the first and second channels may be a plurality of channels extending in parallel. The air flow path includes fins.

The present invention presents a method for solving the above problems. This method includes two parts, and in the first part it is calculated whether the dew point temperature of the air is higher than the temperature of the liquid. This is done in the following steps:
Calculate the dew point temperature of the ambient air, that is, the air dew point temperature before the air enters the first heat exchange stage,
The calculated dew point temperature of the air is compared with the temperature of the liquid measured or transmitted by the host control device.

The dew point temperature of air is calculated, for example, as follows:
The air temperature and humidity are measured before the air enters the first heat exchange stage, and the air dew point temperature is determined from the measured air temperature and humidity.

In order to specify the dew point temperature of air from the measured temperature T and measured humidity of the air, for example, a Mollier diagram can be used. The dew point temperature (abbreviated as Tpl)

Where the temperature units T and Tpl are in degrees Celsius, and the air humidity phi is used as a relative percentage of air humidity.

  It is also possible to measure two different values of the hx-diagram of air (h is enthalpy, x is absolute humidity), for example, dry bulb temperature, wet bulb temperature, intrinsic enthalpy and air Two numerical values are calculated from the density, and the dew point temperature of the air is calculated therefrom.

The second part of the method is carried out, where the heat exchanger is operated in an operating mode called pulse operation, when and during the time when the dew point temperature of the air is higher than that of the liquid. Pulse operation includes the following steps that are repeated in the same sequence in succession:
Liquid flows through the first heat exchange stage for a predetermined period of time,
The liquid is prevented from flowing through the first heat exchange stage, and the air temperature is measured and monitored after exiting the first heat exchange stage, with the measured air temperature after exiting from the first heat exchange stage. Shows a first temperature rise, then stays at a roughly constant level (corresponding to the wet bulb temperature of the supply air) for a certain period of time, and then shows a second temperature rise,
A second temperature rise is detected, and the second temperature rise is terminated to prevent the liquid from flowing through the first heat exchange stage after the detection, and this process is such that the air dew point temperature is less than the liquid temperature. Repeated for high.

  In pulse operation, the condition of whether the dew point temperature of the air is higher than the temperature of the liquid by carrying out the first part of the method is checked periodically or aperiodically.

  In the pulse operation, a phase in which condensed water is removed by vaporization is periodically performed following the phase in which condensed water is accumulated, while air cooling is continued without interruption. In pulse operation, water temporarily accumulates between the fins, but the clogging of the fins with condensed water, which can cause the air flow to be stopped, is prevented, and the heat exchanger is reduced by reducing the water flow interruption time to a minimum. Efficiency is improved.

  In order to be able to carry out the method according to the invention, the heat exchanger is equipped with the necessary temperature and humidity sensors.

  If the heat exchanger includes a second active stage in which heat is pumped between the liquid and air by the inflow of energy, the first is achieved by preventing the liquid from flowing through the first heat exchange stage. According to a variant of the second variant, the liquid does not flow through the second heat exchange stage and the second heat exchange stage is blocked or the liquid is prevented from flowing through the first heat exchange stage. Accordingly, the liquid is guided around the first heat exchange stage (bypass), so that the liquid can nevertheless flow through the second heat exchange stage.

  The invention is explained in detail below using examples and figures. The figure does not match the actual size.

FIG. 2 is a schematic side view or plan view of a portion of a gas-liquid heat exchanger that is arranged to operate according to the method according to the invention and is necessary for understanding the invention. FIG. 2 is a schematic side view or plan view of a portion of a gas-liquid heat exchanger that is arranged to operate according to the method according to the invention and is necessary for understanding the invention. FIG. 3 is a diagram illustrating the method according to the invention.

  1 and 2 show the gas-liquid heat necessary for understanding the present invention, comprising a first passive heat exchange stage 2 and an optional downstream connected active heat exchange stage 3. It is a typical side view thru | or top view of the part of the exchanger 1. FIG. The first heat exchange stage 2 comprises at least one, preferably a plurality of air channels 4 and at least one, preferably a plurality of liquid channels 5. The air flow path 4 and the liquid flow path 5 are alternately arranged in order, and are separated by a thermally passive partition wall having high thermal conductivity. The air flow path 4 includes a plurality of fins 6 that are thermally well connected to a thermally passive partition wall. The spacing between the fins 6 is small so that heat exchange between air and liquid is efficient. The air channel 4 extends in the vertical direction in this example.

  The optional, second, active heat exchange stage 3 can be variously formed. This stage can be, for example, a cooling circuit with a compressor through which the coolant circulates, where the air exchanges heat with the cooling circuit.

  In the example shown in FIGS. 1 and 2, the second heat exchange stage 3 is such that heat can be exchanged between the liquid and air by the inflow of electrical energy, ie by the use of at least one Peltier element 10. Is formed. The second heat exchange stage 3 includes at least one air flow path 7, at least one liquid flow path 8 and at least one Peltier element 10 disposed between the Peltier elements. If it has to be heated, heat is pumped from liquid to air, and if it has to be cooled, heat is pumped from air to liquid. The liquid is not subject to a change in physical state in this example. In the example shown, air flows between parallel fins 9 that are in good thermal contact with at least one Peltier element 10.

  In addition, the heat exchanger 1 includes a valve 11 and an optional bypass line 12, the purpose of which will be described below.

  The term “Peltier element” is often used synonymously in the technical field with the term “thermoelectric element” or the term “Peltier heat pump”. The thermoelectric element is based in particular on the Peltier effect, but may also depend on other electrothermal effects, such as the principle known as the thermal tunnel effect (English is “thermo tunneling”).

  The heat exchanger 1 includes an inlet 13 and an outlet 14 that can be connected to an external liquid circulation system. The liquid circulating in the liquid circulation system is heated or cooled to a predetermined temperature by an external central device. The liquid used is usually water or a water-based liquid, but other suitable liquids may be used. The air flow path 4 extends in the vertical direction. The liquid flow path is designed as a pipeline system, which connects the inlet 13 and the outlet 14 to each other. In addition, the heat exchanger 1 includes a blower and the necessary guide plates and guide elements for forcing the air through the first heat exchange stage 2, if present, the second heat exchange stage 3, And a condensate outlet 15 produced in the second heat exchange stage 3. The liquid flow direction is indicated by arrow 16 and the air flow direction is indicated by arrow 17.

  The heat exchanger 1 further comprises the sensors necessary for the operation according to the invention, i.e. at least one temperature sensor 18 for temperature measurement and a humidity sensor 19 for air humidity measurement arranged before the first heat exchange stage 2; An air temperature measuring temperature sensor 20 and a control device 21 are disposed after the first heat exchange stage 2. The temperature of the liquid is measured, for example, using a temperature sensor 22 located at the inlet or transmitted from an external central device to the control device 21. The control device 21 evaluates the data transmitted from the sensor and controls not only the flow of liquid through the first heat exchange stage 2 but also at least one Peltier element 10.

  FIG. 3 shows three overlappingly arranged diagrams, illustrating the following features of the method according to the invention using examples as a function of time t.

The middle diagram shows the flow of liquid through the first heat exchange stage 2. Flow of liquid through the first heat exchange stage 2, respectively during the predetermined period of time T _1, is flowed, then interrupted, the interruption of the time flow of liquid through the first heat exchange stage 2, valve 11 is closed or the valve 11 is switched if there is a bypass line 12 so that the liquid flows through the bypass line 12 and is thereby guided around the first heat exchange stage 2.

  The bottom diagram shows that the flow through the at least one Peltier element 10 interrupts the flow of liquid through the second heat exchange stage 3 if the flow of liquid through the first heat exchange stage is interrupted. Is done. Each of the flows flowing through the at least one Peltier element 10 is interrupted at the same time if the flow of liquid through the first heat exchange stage 2 is interrupted, or a period of time so that the at least one Peltier element 10 does not overheat. Shut off with a delay. In other cases where the flow of liquid through the second heat exchange stage 3 is not interrupted, at least one Peltier element 10 is not interrupted.

  The upper diagram shows the temperature change of the air after leaving the first heat exchange stage 2, ie the temperature change measured by the temperature sensor 20. A first temperature increase 23 (in the example from 18 ° C. to about 22 ° C.), a substantially constant level 24 and a second temperature increase 25 (in the example from about 22 ° C. to about 27 ° C.) are clearly visible.

The temperature change shown in the upper diagram is composed of the following repeated phases AD.
Phase A: The flow of liquid through the first heat exchange stage 2 is not interrupted: the air is cooled (in the example about 18 ° C.). As time passes, water condenses between the fins 6 and the air flow resistance gradually increases.
Phases B to D: The liquid flow through the first heat exchange stage 2 is interrupted.
Phase B: The temperature of the air rises to a nearly constant level 24.
Phase C: Air temperature remains at level 24. This is because the water collected between the fins 6 is vaporized and the air is adiabatically cooled.
Phase D: As soon as the water between the fins 6 is vaporized, the temperature of the air further increases.

  In FIG. 3, pulse operation can be seen very well. Because the duration of individual cycles (one cycle includes a sequence of phases A to D) is typically in the range of minutes or tens of minutes, and the dew point temperature of air generally changes only slowly. The dew point temperature is re-measured only occasionally during pulse operation, for example, once every 30 minutes, once every hour, or at other time intervals.

Claims (4)

In at least a first, passive heat exchange stage (2), air flows through at least one first flow path (4) with fins (6) and liquid flows into at least one second flow. In a method of operating a gas-liquid heat exchanger flowing through a channel (5), the second channel being separated from the at least one first channel (4) by a thermally passive partition, the following: Procedure steps:
Calculation of the dew point temperature of the ambient air,
Identifying whether the dew point temperature of the ambient air is higher than the temperature of the liquid and, if higher, operating the heat exchanger in an operating mode called pulsed operation according to the following steps:
Allowing the liquid to flow through the first heat exchange stage (2) for a predetermined period of time;
The liquid is prevented from flowing through the first heat exchange stage (2), the temperature of the air is measured and monitored after leaving the first heat exchange stage, in which case the first heat exchange stage (2) is measured after flowing out. Air temperature shows a first temperature rise, then stays at a roughly constant level for a certain period of time, then shows a second temperature rise,
The second temperature rise is detected, and after the second temperature rise is detected, the liquid is stopped from flowing through the first heat exchange stage (2), and this process is the dew point of the ambient air Repeated as long as the temperature is higher than the temperature of the liquid,
A method of operating a gas-liquid heat exchanger characterized by   By measuring the temperature of the air and the humidity of the air before the air flows into the first heat exchange stage (2), the dew point temperature of the ambient air is communicated, and the dew point temperature of the air is the measured temperature of the air and the measured humidity. The method of claim 1, identified from   In a second, active heat exchange stage (3), in which heat is pumped between the liquid and air by the inflow of energy, the liquid is prevented from flowing through the first heat exchange stage (2). The method according to claim 1 or 2, characterized in that the liquid does not flow through the second heat exchange stage (3) and the second heat exchange stage (3) is interrupted.   In a second, method in which heat is exchanged between the liquid and air in the active heat exchange stage (3) by inflow of energy, the liquid is prevented from flowing through the first heat exchange stage (2). Wherein the liquid bypasses the first heat exchange stage (2), so that the liquid can nevertheless flow through the second heat exchange stage (3). 2. The method according to any one of 2.