JPH0373813B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an enthalpy output device that calculates and outputs enthalpy from the temperature and relative humidity of humid air. To find the enthalpy of humid air, the following formula is generally used within the range of temperature and pressure used in general air conditioning. i ₌ 0.240t + (597.3 + _0.441t ) [Kg/Kg'] P is atmospheric pressure [mmHg], _hs is saturated vapor pressure [mmHg], is relative humidity [%], and i is enthalpy [kcal/Kg']. Therefore, conventionally, in order to determine the enthalpy of air, in addition to the dry bulb temperature, absolute humidity,
Alternatively, it was necessary to obtain wet bulb temperature, relative humidity, dew point temperature, etc. Although the method of determining dew point temperature or absolute humidity is relatively easy to calculate, it has drawbacks such as slow reaction speed of the detection element and expensive element. In addition, methods for determining wet bulb temperature and relative humidity have the disadvantage that the calculation formulas are complicated, and therefore the equipment that executes the calculations is also complicated. The present invention uses dry bulb temperature and relative humidity, which are important elements of air conditions in living environments, to calculate enthalpy in a wide temperature range such as indoor air conditions (approximately 20°C to 30°C) in health air conditioning and outside air conditions. The present invention provides a device that sets the equation (c), performs calculations on this equation, and outputs enthalpy. i=(at ² +bt+c)+mt+n...(c) Here, a, b, c, m, and n are constants. If the enthalpy value is determined by the arithmetic device that executes the calculation formula (c) according to the present invention, there is no need to perform the conventional complicated calculations using the formulas (a) and (b), and the practical temperature range in which the enthalpy calculation can be performed is achieved. It is easier to obtain more accurate values than reading from a psychrometric chart. Next, we will explain how to derive the arithmetic expression (c). In the hygrodynamic diagram (i-x diagram) and basic formulas (a) and (b) for enthalpy calculation, it is difficult to express enthalpy as a simple relational formula between relative humidity and dry bulb temperature, but dry bulb temperature can be expressed as When it is held constant, enthalpy i can be approximated by a linear function of relative humidity as shown in FIG. 1, so it can be expressed by equation (2). i=α+β...(d) Here, α and β are constants. Next, if we create an approximation equation (D) for each temperature and consider the changes in each coefficient α and β with respect to temperature, the coefficient α is a quadratic function (H) of the temperature t, as shown in Figure 2.
It was found that the coefficient β can be approximated by a linear function (F) of the temperature t as shown in Figure 3. α=at ² +bt+c...(e) β=mt+n...(f) Here, a, b, c, m, and n are constants. Therefore, by substituting equations (e) and (f) into equation (d), equation (c) is obtained. Equation (g) shown below is an arithmetic expression in which constants are determined over a temperature range of 5°C to 35°C. i=(1.692×10 ⁻⁴ t ² −8.140×10 ⁻⁴ t +0.03753)+0.2326t+0.1054 (G) Next, how to obtain equation (G) will be explained. In the basic formulas (a) and (b), the relationship between relative humidity and enthalpy i is determined with the dry bulb temperature constant, and the relative humidity is 30% and 70%.
From the enthalpy value when , approximate with a linear equation.
For example, when the dry bulb temperature is 20°C, the relationship between enthalpy i and relative humidity is expressed by equation (H). i=0.08898・+4.757...(H) Similarly, find the linear equation for the dry bulb temperatures of 10℃, 15℃, 25℃, and 30℃. Next, the coefficient α for each temperature,
By approximating β using the least squares method, α is (re)
Equation, β can be expressed as (nu) equation. α=1.692×10 ^-4 t ² −8.140 ×10 ^-4 +0.03753 ……(li) β=0.2326t+0.1054 ……(nu) Therefore, from equations (li) and (nu), (g) A formula is required.
Table 1 shows a comparison of the accuracy between the calculation formula (g) and the basic formulas (a) and (b).The enthalpy difference is 0.5 or less over the entire range, which is highly accurate, and within the range of practical temperature and relative humidity. The accuracy is sufficiently high.

[Table] Next, an embodiment of an enthalpy calculation device that performs the calculation expressed by the calculation formula (g) will be described based on FIGS. 4 and 5. When performing calculations with an arithmetic circuit,
Equation (L), which is a rewrite of Equation (C), is convenient. i=(at ² +bt+c)+mt+n =a・{(t+p) ² +q}・+mt+n
...(l) Next, one embodiment of the present invention will be described. FIG. 4 is a basic diagram of the present invention. In the figure, 1 is a humidity signal output section equipped with a humidity sensor, which outputs a voltage proportional to relative humidity. Reference numerals 2 and 3 are temperature signal output sections, and the degree of amplification is changed by a resistance expressed by a linear function with temperature as a variable. Reference numerals 5 and 6 denote first and second multipliers for multiplying the temperature signal and the relative humidity signal. Here, since the multipliers 5 and 6 are installed in series, the output of the multiplier 6 can be expressed as the product of the relative humidity signal and the square of the temperature signal. An adder 7 adds the output signal of the multiplication section 6 and the output signal of the temperature signal output section 4, and outputs an enthalpy value to the output section 8 as a voltage value. FIG. 5 shows a specific configuration of one embodiment of the present invention shown in FIG. 4, in which reference numeral 9 denotes a humidity signal output section consisting of a humidity sensor 10 that detects humidity changes as resistance changes and a resistor 13 connected in series. It is. Terminal 11
The voltage value is a value obtained by dividing the voltage value applied to the terminal 12 by the ratio of the resistance 9 and the resistance 13 of the humidity sensor 10, and can be expressed as a voltage proportional to the humidity sensor 10, that is, relative humidity. 14,1
5 and 16 are resistors that act in cooperation with the temperature sensors 17, 18, and 19 and elements such as resistors connected to each, and are used as multipliers, each representing a resistance value expressed as a linear function of temperature. When a voltage proportional to the relative humidity is input to the input terminal 11 of the operational amplifier 20 as the first multiplier,
A voltage corresponding to the amplification determined by the resistor 21 and the resistor 17 of the temperature sensor 14 is output to the terminal 22 . Here, if the combined resistance 14 of the temperature sensor is expressed as a linear function with temperature as a variable, the output voltage of the terminal 22 can be expressed as the product of the relative humidity and the linear function of temperature. Similarly, the multiplication by the operational amplifier 23 as the second multiplier causes the operational amplifier 23 to
The voltage at the output terminal 24 of can be expressed as the product of the square of a linear function of relative humidity and temperature. By placing the voltage output unit 25 in the negative feedback circuit of the operational amplifier 23, constant correction corresponding to β in the arithmetic expression (L) can be performed. The operational amplifier 26 is an adder, and adds the voltage at the terminal 24 and the voltage value at the terminal 29, which is represented by the voltage obtained by dividing the voltage applied to the terminal 27 by the ratio of the resistor 16 of the temperature sensor 16 and the series resistor 28. , outputs the enthalpy value to the terminal 30 as a voltage value. As mentioned above, the enthalpy output device of the present invention, which uses the method of deriving the enthalpy value by executing the arithmetic expression (R), is composed of a temperature sensor, a humidity sensor, and a calculation section, as shown in the embodiment, and does not require an electronic computer. In addition, it is possible to create an inexpensive arithmetic device consisting of a simple arithmetic circuit with a small number of constituent elements. As mentioned above, the enthalpy output device of the present invention is
n, a method that calculates from a simple formula using dry bulb temperature and relative humidity, which are the most important environmental indices, as variables.
Since it is a device, once dry bulb temperature and relative humidity are detected, other factors such as saturated vapor pressure can be calculated directly without the need to search for approximations or conversion tables. Further, the enthalpy output device according to the present invention can easily calculate values with high precision even when calculating with an electronic computer etc. by programming the calculation section of the temperature signal and humidity signal. In addition, this computing device can output the enthalpy value, which is the thermal energy held by the air, as an electrical signal from the temperature and relative humidity that are directly targeted when performing air conditioning, so it can be used for automatic control of air conditioning. It has great advantages such as being easy to do. Furthermore, since this device has fewer components, it is possible to realize an enthalpy output device with a simple configuration.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between relative humidity and enthalpy, Figure 2 is a graph showing dry bulb temperature and coefficient,
FIG. 3 is a graph showing the relationship between dry bulb temperature and coefficient β, FIG. 4 is a basic configuration diagram of an embodiment of the present invention, and FIG. 5 is an electric circuit diagram of the embodiment. 10... Humidity sensor, 17, 18, 19... Temperature sensor, 20, 21, 26... Operational amplifier.

Claims (1)

[Claims] 1. A humidity sensor that converts relative humidity into a humidity signal, a temperature sensor that converts temperature into a temperature signal, a first calculation means that receives the temperature signal as input and derives a quadratic function of the temperature signal, and the first a second calculation means that derives a product signal of the output of the calculation means and the humidity signal; a third calculation means that also derives a linear function of the temperature signal; and an output of the second calculation means and the third calculation means. An enthalpy output device having an arithmetic unit including a fourth arithmetic means that adds the outputs of the two and outputs the result as an enthalpy value.