JPS58175797A - Total heat exchanger element - Google Patents

Abstract

PURPOSE:To increase the heat exchanging efficiency of a heat exchanger by suppressing the rise of sensible heat caused by absorption of heat which is produced when moisture absorbing substance, being added to the base material, absorbs moisture, by adding a substance which shows a heat absorbing reaction at the time when it is dissolved into water, to the base material of total heat exchanger element. CONSTITUTION:Moisture absorbing substance 2 is deposited on a base material 1, in order to increase the latent heat exchanging efficiency. When an element absorbs moisture from the airflow, first, moisture is adsorbed to the surface of an element, and absorption heat is generated to heighten the temperature of the element. At that time, high temperature generated by absorption of moisture is moderated, because the raised temperature at the time when dissolving reaction is taken place is lowered by a substance 3 such as potassium nitrate or sodium nitrate, which shows heat absorbing reaction at the time when it is dissolved into water, is deposited on the base material 1. Accordingly, the value of heat, transferred by the airflow into the base material 1, is decreased, the exchanging efficiency of sensible heat is increased, while the decrease of moisture-absorbing capacity due to the increase of temperature in the base material 1 is prevented, so that minus influences to the heat exchanging rate in latent heat can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchange element for a total heat exchanger that simultaneously recovers sensible heat and latent heat, and provides a heat exchange element that is more efficient than conventional ones.

Conventionally, total heat exchangers have been of the stationary transmission type or the heat storage rotation type, and in many cases, a hygroscopic substance is added to the base material of the heat exchange element in order to increase the latent heat exchange efficiency. However, conventionally used materials generate heat when they absorb moisture, and this heat enters with the airflow, which has a negative impact on sensible heat exchange efficiency and hinders efficiency gains. . In addition, this heat generation increases the temperature of the surface of the base material, resulting in a decrease in moisture absorption ability and adversely affecting the latent heat exchange efficiency.

The present invention relates to a heat exchange element that alleviates such problems, and aims to provide a heat exchange element that reduces heat generation during moisture absorption and is more efficient than conventional heat exchange elements. In other words, conventional total heat exchange elements are made by impregnating a base material such as paper, asbestos paper, or plastic paper with a hygroscopic substance such as lithium chloride, or by impregnating alumina on the surface of aluminum.

Those coated with a hygroscopic substance such as silica are often used. In these cases, when the element absorbs moisture from the airflow, the moisture is first adsorbed onto the surface, generating heat of adsorption and increasing the temperature. Next, when a deliquescent substance such as lithium chloride is used as a hygroscopic substance, a phenomenon of dissolution in these water molecules occurs. At this time, since lithium chloride and the like exhibit an exothermic reaction, the temperature will further rise. However, if a substance that exhibits an endothermic reaction when dissolved in water is added to the base material, the temperature during the dissolution phenomenon will drop.
This will reduce the high temperatures caused by adsorption.

Hereinafter, one embodiment of the present invention will be described based on the drawings. Figure 1 shows a hygroscopic material 2 on a base material 1, which is commonly used in the past.
FIG. 4 is a schematic cross-sectional view of a part of the total heat exchange element plate when the total heat exchange element plate is added. FIG. 2 shows a schematic cross-sectional view of a part of a total heat exchange element plate according to an embodiment of the present invention. Power IJ (
KNO3) or sodium nitrate (NaNO5)
This is the case when substance 3 such as the following is added. The base material may be paper, metal, plastic, or a composite thereof, and its shape may be various, such as one in which flat plates and corrugated spacers are alternately laminated, or a honeycomb shape.

In order to confirm the effect of the total heat exchanger according to the present invention, an apparatus as shown in FIG. 3 was used. In Figure 3, 4 is the louver (front panel), 5 is the frame, 6 (d, 7')
7 is a fan motor, 12 is a total heat exchange element. Here, the fan 6 is turned on for a certain predetermined time (
For example, the rotation is reversed every minute) and the wind direction is changed.
Moisture absorption and dehumidification in the total heat exchange element are performed alternately.

The total heat exchange element has a height of 25c11. It has a width of 25 mm and a depth of 6 mm, and consists of alternating layers of kraft paper flat plates and corrugated spacers, and is impregnated with lithium chloride as a hygroscopic substance. Table 1 shows a comparison with the case where a substance exhibiting an endothermic reaction when dissolved in water was added. The processing air volume was 2 m/min, the switching cycle was at 1-minute intervals, and the test conditions were: 33°C, 170% (relative humidity) outside, assuming indoor cooling in the summer;
The temperature inside the room was 26°C and 50% RH.

As shown in Table 1, it can be seen that it is more effective to add a substance that exhibits an endothermic reaction when dissolved in water. Looking at this in more detail, in the case of an element to which only a hygroscopic substance is added, first high temperature and high humidity outside air of 33°C and 70% RH is sucked in by a fan, and the total heat exchange element board passing through contact. The change over time in the temperature of the air flow at the outlet of this element is caused by the fact that, due to the heat capacity of this element, a part of the sensible heat of the air and flow is stored, and a part of the large adsorption heat generated by moisture absorption is also stored. 33°C due to heat storage
When the heat capacity of the element reaches saturation, the heat of adsorption during moisture absorption is added to the sensible heat of the airflow, and after 1 minute, the heat capacity of the element reaches saturation.
The temperature rises to 4.6℃. On the other hand, if we look at the change in moisture absorption in the element over time, it is initially after desorption, so the amount of residual adsorption is small, and the surface temperature of the element plate is low, so the water vapor pressure on the element plate surface is higher than that of the air flow. Moisture absorption progresses, but as time passes, the amount of moisture absorbed increases and the surface temperature rises due to the exothermic reaction during adsorption.
The water vapor pressure at the surface is also increased and moisture absorption is reduced. 1
After a few minutes, the direction of rotation of the fan will be reversed, reducing the low temperature in the room.
In this case, the temperature and humidity conditions of the air flowing out of the room are different, and when the outdoor air is taken in after another minute, the element is in a better condition. The question is whether the conditions are met. The element, which had risen to around 34.6°C, was cooled by indoor air at 26°C and 50% RH, and the temperature decreased due to the heat of desorption of moisture, and the airflow after passing through the element after 1 minute was The temperature is 24
．． The temperature will be 6°C. From the point of view of heat capacity, the lower the element temperature, the better, but from the point of view of moisture absorption and desorption, if the element temperature is low, dehumidification will be insufficient and this will be a factor in reducing the amount of moisture absorbed in the next cycle. There is. On the other hand, when both a hygroscopic agent and a substance that exhibits an endothermic reaction when dissolved in water are added, the heat of adsorption generated by moisture absorption when outdoor air is taken in is softened by the endothermic reaction during dissolution, so even after one tray KNO3te is 33.6°C, NaNOs is 33.7°
C, which is approximately 1°C lower than when using the hygroscopic substance alone. Furthermore, the amount of moisture absorbed in the element is also greater than in the case of a hygroscopic substance alone, since the rise in the surface temperature of the element plate is small. Note that since substances that exhibit an endothermic reaction during dissolution also have hygroscopic properties, this factor is also included in the increase in the amount of hygroscopic absorption. In addition, when the fan rotates in the opposite direction and the indoor air flows out, the temperature of the airflow 1 minute after switching is KNO.
3: 26.5°C; NaN03: 25.3°C, which is not good in terms of the heat capacity of the element, but has a better effect on dehumidification than the case of a hygroscopic substance alone.

The above describes the case where the total heat exchange element is fixed and the rotational direction of the fan is reversed every cycle to repeat moisture absorption and desorption. The same can be said of the total heat exchange element.

As described above, according to the present invention, by adding a substance that exhibits an endothermic reaction when dissolved in water to the base material of the total heat exchange element, the increase in sensible heat due to the heat of adsorption generated with moisture absorption can be alleviated. In turn, the moisture absorption capacity can be improved, and a highly efficient total heat exchange element can be achieved.

[Brief explanation of the drawing]

Figure 1 is a partial sectional view of a conventional total heat exchange element in which a hygroscopic substance is added to the base material, and Figure 2 is a partial sectional view of a conventional total heat exchange element in which a hygroscopic substance and water are added to the base material in an embodiment of the present invention. Partial cross-sectional view of the total heat exchange element when an endothermic reaction is added during melting, Part 3
The figure is a schematic cross-sectional view of a simple total heat exchange ventilation fan used in the evaluation test. 1... Base material of total heat exchange element, 2... Hygroscopic substance, 3... Substance that exhibits an endothermic reaction when dissolved in water, 5...・Frame, 6...Propeller fan, 7...Fan motor, 11...
...Intake/exhaust port, 12...Total heat exchange element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure? Figure 2 Figure 3

Claims (2)

[Claims] (1) A total heat exchange element in which elements to which a substance exhibiting an endothermic reaction when dissolved in water is added to a base material are arranged at predetermined intervals. (2) A total heat exchange element in which elements to which a substance exhibiting an endothermic reaction when dissolved in water and a hygroscopic substance are added to a base material are arranged at predetermined intervals.