IL47511A - Calorimeter - Google Patents

Description

C A L OR I M R mo The concerns a calorimeter for measuring the quantity of heat given off by a flowing which oomprlees temperature measuring means for measuring the difference between the temperatures of the inflow and the outflow of the volume measuring means for measuring the volume of the flowing medium as well as means for calculating the quantity of heat given off from the difference of the temperatures and the volum In known devices of this which calculate the quantity of heat given off only from the difference of the temperature and the an error is made since the thermal capacity of the medium particularly when considering water varies not entirely nificantly with the The exact expression for the quantity of heat given off is given b wherein T time enthalpy of the forward flow of the water enthalpy of the return flow of the water a mass of the water when in the expression the substituted k da dv wherein At is the temperature difference between the nflow temperature and the outflow temperature v the or the it follows that As can be expression oontains Just the two quantities which are measured directly in the known the temperature difference t and the v of the In the known it is customary to assume k with the temperatures used k deviates very considerably from the value a fairly large inaccuracy is introduced This mistake somewhat when instead of the value 1 a somewhat lower value is assumed for k A satisfactory accuracy is hereby also not because k varies with the temperature of the since it also holds that which expression the thermal capacity of the as well as the speclflo gravity of the water vary with the water As can be seen from the it has been desired to produce a calorimeter with simple means in while taking the variation of the with the temperature into a substantially more exact measurement of the quantity of heat can be carried out than with the devices known up to and it the object of the present invention to provide such a To solve this the calorimeter according to the invention in that the temperature measuring means measure the outflow temperature and that means are provided which correct the calculated quantity of with the of a linear correction value k which le dependent on the outflow taking Into consideration the specific heat and the specific gravity of the medium which change with The Invention s based on the surprising discovery that owing to the that the ctor s permitted to vary In a suitable manner In linear dependence on the outflow such a correction of the measured quantity of heat can be obtained that t s very close to the values calculated exactly from the measured results within a very large range of outflow temperatures and differences of This will be further explained herelnbelow with reference to the Since here a question of a linear t can be carried out with extremely simple In the case where the temperature means produce a first electric signal linearly dependent on the difference In temeprature and where the volume measuring means produce a second electric signal linearly dependent on the and where the calculating means combine the first and the second signal for the purpose of producing an indication of the quantity of heat given the temperature measuring according to the may produce addition a third signal linearly dependent on the outflow and means may be provided which bring about that the third signal has a linear influence on the first second As oan be the correction obtained in case an extremely simple A practical embodiment of such an wherein the first signal consists of a plurality of short whose repeater frequency linearly dependent on the difference in wherein the seeond signal a plurality of whose number is linearly dependent on the and wherein the calculating means count the number of pulses in the first which occur in the presence of the pulses the seeond characterized according to the invention in that the third signal is led to the volume measuring means which are arranged so that the pulses of the second signal each have a duration which varies linearly with the third such an the volume measuring means can according to the a each after a given volume has been is triggered and thus gives off a pulse whose duration is determined by the third The described more clearly the following by means of the schematic shows a wiring diagram for one embodiment of a calorimeter according to the and show several curves which contribute to the further explanation of the a heat eonsumer 1 is drawn to which warm water led via pipe and which gives off slightly cooler water via a pipe In pipe 2 a first feeler 4 is disposed which converts the temperature of the water in the 2 an electric which fed into a converter A second feeler provided in the pipe 3 and converts the temperature of the return flow water into a second electric which likewise is fed into the converter converter 5 give at its output an signal whose repeater frequency 5 is proportional to the difference between the inflow temperature the return flow temperature f which expression is a proportionality The volume of the water flowing through the heat consumer 1 is measured by means of a device 6 measuring the quantity of The device 6 gives off a pulse to a monostable each time after a predetermined volume of water has flown through The triggered by each incoming pulse and then gives off at its exit a pulse whose duration is independent from the shape of the pulse and is of such that it encompasses a substantial number of pulses appearing at the exit of the converter The exit signal of the converter 5 is led by a lead 8 to a first inlet of a counter 9 and the exit signal of the 7 by a lead a second inlet of this The counter 9 arranged so that It counts the number of which are led in the course of the duration of the pulses through the lead 10 to the first inlet through the lead By means of suitable conversion of the number of counted pulses and by suitable dimensioning of the described switching possible to obtain a result of the measurement which can he wth the aid of an Indicating element an magnetic and which give expression to that quantity of heat which Is given off by the medium to the heat consumer the switching above described the mentioned variation of the specific gravity and the thermal oapaolty of the water with the temperature of the water not yet been taken Into measuring results obtained oan thus only be correct for a definite difference between the Inflow and return flow difference and a definite temperature of the 2 Illustrated how the specific gravity of the water changes wth the temperature t of the Illustrates In corresponding how the thermal oapaolty varies Since the specific heat s based on the aass of the water and this Is the volume of the which oan be measured by the measuring can be seen that actually It could be expected that an extremely complicated correction must be to obtain a suitable conformity between the measuring results and the actual It has thus been extremely surprising to that by means of a relatively simple correction an excellent approximation of the exact conditions oan be Is Illustrated more clearly In 4 which shows the variation of the wth the temperature of the return flow water for various values of the temperature differeone calculated values are Illustrated n 4 by fully drawn This figure contalne besides a straight line which s shown In dashed lines and which can be expressed by k m It can be seen that this line represents an evoellent approximation to the exact and should be mentioned especially that it is here a of an approximation which is considerably better than the constant value for k of which was mentioned in the beginning and used up to now and is likewise shown a dashed line in the approximate correction by a linearly is realized in an extremely simple manner in the arrangement 1 that the signal coming the temperature sensor which represents the return flow temperature led by a lead 12 to the mul 7 a control voltage which controls the duration of the exit pulses of the This durationT can be expressed by in which expression and are constants and the value which parenthesis represents the mentioned Αβ can be seen from the with the described arrangement a calorimeter obtained which by using extremely simple means take account the specific gravity and thermal capacity of the water which varies with so that a measuring result is obtained which corresponds the exact value with extremely approximatio In besides the parts described a lead 13 drawn which feeds the signal from the measuring device 6 to a element an which built into the same instrument together with the element is in no way limited to the diment illustrated the drawings and above but may be changed in numerous ways within the work limited by the ollowing insufficientOCRQuality

Claims (2)

1. Calorimeter for measuring the quantity of heat given off by a flowing medium, which comprises temperature measuring means (4,5,4* ) for measuring the difference between the inflow temperature and the outflow temperature of the medium, volume measuring means (6,7) for measuring the volume of the flowing medium, as well as measn (9, 10) for calculating the Quantity of heat from the difference of the temperature and volume, characterized in that the temperature measuring means (4,5*4· ) measure the outflow temperature (tg) and that means (12,7) are provided which correct the calculated quantity of heat with the aid of a linear correction value (k) which is dependent on the outflow temperature talcing into consideration the specific heat (cp) and specific gravity {J* ) of the medium which change with the temperature.

2. Calorimeter as claimed In claim 1, wherein the temperature measuring means produce a first electric signal dependent linearly on the difference in temperature, wherein the volume measuring means produce a second electric signal linearly dependent on the volume and wherein the calculating means combine the irst and the seoond signal for the purpose of produolng an Indication of the quantity of heat given off, characterized in that the temperature measuring means (4, 5. 41 ) produce in addition a third signal linearly dependent on the outflow temperature (t^) and in that means are provided which bring about that the third signal has a linear Influence on the first 3« Calorimeter as claimed In claim 2, wherein the first signal consists of a plurality of short pulses, whose repeater frequency (f) is linearly dependent on the difference in temperature (^t), wherein the eeoond signal Is a plurality of pulses, whose number Is linearly dependent on the volume, and wherein the calculating means count the number of pulses in the first signal, which occur in the preeence of the pulses in the second signal, characterized in that the third signal is led to the volume measuring means (6, 7)» which are arranged so that the pulses of the seoond signal each have a duration (" ) which varies linearly with the third signal* 4· Calorimeter as claimed in claim 3» characterized in that the volume measuring means (6,7) comprise a monostablle multi-vibrator (7) which, each time, after a given volume has been measured, is triggered and thus gives off a pulse whose duration ( ^ ) determined by the third signal. AGENT FOR APPLICANTS