METHOD AND APPARATUS FOR DETERMINING HEAT LOSS

Abstract: Method and apparatus for determining the heat loss of for instance a human or a heated building depending upon the current climate. The principle is based upon an analogue method of simulation and includes a heated climate sensing body. The heat flow is being simulated by a corresponding electric current (1). The skin's respectively the wall's thermal resistance is being simulated by a corresponding electric resistance (R). The body temperature and the surface temperature of the skin or the inner- and outer temperature of the wall are simulated by two corresponding potentials (Ub resp Us) appearing on each side of the electric resistance (R). The current (1) is being measured by means of for instance one in the heat flow or in effective temperature calibrated instrument.

Description: - The present invention relates to a method and apparatus for cl±toate measurements such as for detexinining the human heat loss of as well indoor as outdoor climate for the control of climate in buildings. It is since long known that the degree of air movement in particular but also humidity and heat radiation from the sun determines the degree of cooling acting upon both humans and buildings. Bripirical studies made for-instance during admiral Byrd's expedition to the Antarctic in 1939-1941 show that the human experience of for instance an air teπperature 0 C and an air movement 20 m/sec. is equal to a teπperature of -20 C and windstill. Described in the Patent Specifications Nos. SE 7114749-0, DE 1.798.439, DE 2.210.523 and DE 2.528.340 but also in the Swedish Publication 'Ny Teknik , 1973-12, page 5 and in 'Hea ing/Piping/Air Conditioning', January 1973, page 139- 144 as a known method to utilize one electrically heated body as a sensor in an apparatus measuring the degree of thermal discαnfort especially in indoor climate and where the conveyed electrical power is a measure of the heat loss of the body. It is also a known method to supply the climate sensing body with a thermal resistive material in order to simulate the thermal resistance of the human skin. Described in SE Patent Specification No. 7114749-0 is another method for simulating this thermal resistance where the loop gain of the temperature regulation system is being reduced so that a regulation error is obtained. The heat flow which leaves the human body through the skin is to be formulated as Q = (T b - T s )/z 1) OlviPI Λ,_ IPO . Q is the heat flow per unit, area of the human body T is the surface temperature of the skin z is the thermal resistance per unit area of the skin T, is the internal teπperature of the human body, normally 37 C. In an apparatus according to the invention the heat flow is being simulated with an electric current (I) , the thermal resistance of the skin withan electric resistance (R) , the skin's surface with an electric potential- (U ) and the teπperature of the human body with an electric potential (U, ) . The electric current which flows i±irough. th -electric resistance may be formulated as I = (^ - U s )/R 2) The electric resistance (R) together with the two electric potentials (U. ) and (U ) are thus affecting the electric current according to the expression 2) in the same way as the thermal resistance (z) together with the tvo temperatures (T, ) and _,(T ) are affecting the heat flew,according to the expression 1) . If we suppose that the relation between an electric potential and temperature can be expressed as U = k • T 3) where k is a constant we get according to 1) and 2) that the relation between the electric resistance and the thermal resistance may be formulated as R = k - z 4) For a heated building a similar argumentation may be applied. If in this case T indicates the temperature of the wall's surface and T, the temperature of the walls inner surface and z the thermal resistance of the wall then the heat flow Q through the wall will be described according to 1) . based upon the invention. The apparatus is supplied with a constant voltage of for exaπple 5 Volts. The transistor (T1) and the linear teπperature sensor (D1) are thermally connected to each other and also to a climate sensing body "which is affected by the climate one wants to measure. The climate sensing body may in practice be made of a cylinder of metal with the dimensions 010 x 30 urn with a durable surface. The current (I) which flows through the transistor (T1) for instance of type BD 529, will cause that the transistor (T1) but also the teπperature sensor (D1) which in practice can be the silicon diode 1N 914 and the climate sensing body are being heated up to the temperature (Ts) . ϊhe resistor (R1) together with the temperature sensor (D1) will make that one to the teπperature (T ) proportional potential (ϋ ) is obtained. With the two resistors (K2) and (R3) a potential (11 ) is obtained which is proportional to (T, ) . The resistor (R) which is flcwn through by the current (I) simulates the skin's thermal resistance. The current flowing through (R1) and (D1) is as well as the current through (B__ and(R3 much less than the current (Ij and could be entirely neglected. The operational aπplifier (OP1) could for instance be of type 2740. (OP1) has a high aπpli ication for exaπple 100000 times and oont ols the current (I) through the transistor (T1) . With the high aπplificatiαn of the operational amplifier (QP1) tbs voltage difference between the two inputs may be considered to be nil. This allows then the follcwing relation to be formulated v-hich after reforπiilation results in 1 β <°b " ϋ s ) R i.e. an expression identical to 2) above. The heat flow according to expression 1) can thus simply be measured with an apparatus according to the invention by utilizing one, for instance in a heat flew, Clo-units, or in the equivalent teπperature of a stationary air volume calibrated instri rent OMPI which measures the current (I) and where the thermal resistance is determined by the electrical resistance (R) . The apparatus described has considerable advantages to those described in the Patent Specification mentioned in the introductory paragraphs. According to the present invention the skin's thermal resistance is being simulated with an electrical resistance. This method is considerably siπplier to apply and results in a greater precisian in the simulation than the method of furnishing the climate sensing body with a heat insulating layer. It is difficult to furnish a climate sensing body with a defined layer which has a durable surface which has stable thermal qualities and which has a defined and constant thermal connection to the climate sensing body. In the Patent Specification SE 7114 749-0 the thermal resistance is being simulated with partly a heat insulating layer but also partly owing to the fact that the locp gain of the taiperature regulation system is being reduced so that a certain regulation error will occur. The way of the present invention is even in this case considerably siπplier to apply and will result in a greater precision in the simulation of the thermal resistance. According to well kntwn theories of feedback control systars, a low loop gain will result in substantial regulation errors. In general this is not wanted as irrelevant parameter variations in the systan will influence the regulated or simulated quantity in a negative way, but also that the regulated or simulated quantity in itself not beccmes entirely defined. In an apparatus according to the invention the influence of-the human perspiration on the heat loss to the envirt-nment is simulated allowing water to evaporate from the surface of the climate seising body with a porous surface which is being moistened with water. Depen i g on the humidity of the surrounding air mass a more or less rapid evaporation of the water will occur. This effect will cause a more or less great heat loss from the climate sensing body. In an apparatus according to the invention the effect of air movement is regulated by means of a suitably formed shield which to the extent desired limits the cooling of the climate sensing body. The shield can for instance be made of a fine- meshed net or a in a suitable way perforated can which encloses the climate sensing body. OMPI

Claims: CLAIMS 1. Method for determining heat loss especially with humans but also with buildings c h a r a c t e r i z e d in that the heat flew decipated via the human skin or the wall of the building is simulated by the corresponding electric current (I) , that the thermal resistance of the skin or the wall is simulated fcy a corresponding electric resistance (R) flown through by a current (I) that the human body temperature and the skin surface teπperature or the inner and outer siirface temperatures of the wall are simulated by two corresponding electric potentials (U, ) and (U ) , and that the voltage drop across the electric resistance (R) is regulated to become a certain function of the two potentials ϋ, and ϋ . 2. Method for practising claim 1 c h a r a c t e r i z e d in that the electric current (I) is measured by a device calibrated in teπperature equivalent to the temperature of a still moisture « *» saturated air mass which causes the same degree of heat loss as the actual climate. 3. Apparatus for practising the method according to claim 1 utilizing an electrically heated climate sensing body the teπperature of which is determined by a tsπperature sensor (D1) ch a r a c t e r i z e d in that a transistor (T1) is utilized and that by the current (I) caused power decipation is used for the purpose of heating the climate sensing body, a resistor (R) is utilized for the simulation of the thermal resistance of the skin and wall respectively and that a voltage divider (R2-R3) is utilized for the siπulation of the human body teπperature or the inner surface teπperature of the wall by a proportional electric potential (ty . 4. Apparatus according to claim 3 c h a r a c t e r i z e d in that for the control of the voltage drop across the resistor (R) an operational amplifier is utilized so that the intended function of the * potentials (U. ) and (U ) is achieved. OMPI IPO " 5. Apparatus according to claim 3 or 4 c h a r a c t e r i z e d in that for the simulation of the human perspiration the climate sensing body is so designed that water may evaporate from its surface. 6. Apparatus according to claim 3 or 4 c h a r a c t e r i z e d in that for the control of the influence of air movements on the climate sensing body a suitable designed shield is included. OMPI Λ, IIPPOO .<

Inventors: NILSSON B
Applicants: NILSSON B, THERMIUS ELEKTRONIK
Application year: 1981
Main classification: G01W1
IPC codes: G01K17, G01W1, G06G7