AU601589B2

AU601589B2 - Multiple sheet insulating glass for cold storage chambers

Info

Publication number: AU601589B2
Application number: AU16962/88A
Authority: AU
Inventors: Hans Bause; Rolf Groth
Original assignee: Flachglas Wernberg GmbH
Current assignee: Flachglas Wernberg GmbH
Priority date: 1987-01-02
Filing date: 1988-06-01
Publication date: 1990-09-13
Anticipated expiration: 2008-06-01
Also published as: SE8705192L; SE468861B; IT1215657B; GB8730016D0; SE8705192D0; BE1001694A4; GB2199360A; FR2609285B1; DE3700076C2; GB2199360B; AU1696288A; FR2609285A1; IT8819001A0; DE3700076A1

Description

COMMONWEALTH OFp AU ST RA LI A PATENT ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE

CLASS

INT. CLASS Application Number,: Lodged; Complete Specification Lodged: Accepted: Published: Priority; for ADDRESS OF APPLICANT~; Otto-S Xi~q-om~n~e 10-14, NTV APPLIMAE'-0 E'LACIMAS A4IEWI S$414$CHAFw D-8510 Furth/Baytrn, Rolt GRQOUI ADDMES IVOR SE RVXCE*.

DAVIFeS A COLLISOU, Patent Att reS 1Little C011izu Stroott Melbr~rre# 3000.

COW=E~ SL'ECIMZAIN FOR tHP. IUTW10ZN JMTI TLED; 4t L'flvxn1E sn,8T~$ 10UThA'TINc GLASO 1'QR C014D STORAGE4 CflAWfl Tho folJ~Ov10 atate*Ant 10 4 foll 4IOSQ iption of this Invo*ntlono Anclvdinj4 the boat wthod of pourfoodogn it knvu to UE) $0 ooki 1A THIS INVFNTION relates to a multiple sheet insulating glass for a glazed door which separates a. cold storage chamber hr.ving a relatively low temperature from surroundings having a higher air temperature, the glass comprising an outer sheet fascin_- the surroundings and an inner sheet facing the cold storage space and separated from the outer sheet by means of an Intermed4*ate space which may be subdivided into a plurality of intermediate .tub-spaqes by means, of at least one intermediate sheet, the outer, -surface of the Inner sheet facing away from the intermediate spaoe being exposed to the atmodsphere of the cold atorage oharnher.

Mtl ti pl1e sheet Insulating glasses of the type described above are tised principally f'or vIrdow-ltke doors, which are used to, s -o~tff caold storage chamers. Tt Is, fo r example the ca~se with 4 refrigerated display care, In which a large-area, View ot the goods stored In the cold storage chamber is deosirable ~Q and In which the door can be opened Cor a short time in order to take out frozen goods, Such refrigerated display aaen have !nner temperatures in, the, region of approximately 1,Q% to P, 5 0100 depending upon the qpcii to cton eas of the low teomporature within the display c-ae 1 good thermal insulating of the glazing n eonary In order to keep the ooolig power required 0,-s low an ponssible.

F'or thin reas-on, a multiple sheet insiulating glaq: isv SO0 A 7 benerally used as a glazing for such applications. In practioe a triple structure with two air spaces, each 6 mm wide for example, is used. In this connection an important aspect is the fact that the total thickness of the multiple sheet insulating glass should be as small as possible, so that the resulting glazed doors are not too expensive in constructional terms. A problem with such glazings in refrigerated display cases is the formation of condensation on the side of the outer sheet facing the surrounding room, as a result of w)hich the view of the interior of the display casi is impeded in a '-:,blesome way. With the low temperature irside such refrigerated display oases, the temper;'ture of the outer sheet Is so far below the normal ambie'it temperature in the display room of, approximately 20 2500 that, with the relatively high air humidity of such rooms of approximately 50 it, falls below the dew point temperature and moisture is deposited on the outer sheet. In order to prevent such condensation, the outer sheet of the triple structure Is heated so as to keep its temperature above the critical dew point temperature. The heating takes ,71ice by means of an elctrioally oonducting, light-~ ,.Prmeable coating, which 1s doposIted on the side of the outer sheet facing the air spae, Considerable extra expenditu;re Is Incurred for this heating as a result of the coating, the requisilte current foeds and the elootrical. supply., in addition, thtre Is the energy consumption for this heating, For this reason it w.ou'd In picpeb eial to, have a multiplo sheet lnsulzting glass for the application referred to abOVe In which the degree of~ theral Isult~n~~ o high that th tnmperatoro of~ the Outer Sheet no longer falls, below the critioal dew point temperature and thus the heating of the outer shoot can be Completely dlppon od with or at loasit the temperature of the Outer, Oheet~ qan bo Incro.ased to such an extent A, 1111 3that the requisite heating power is considerably reduced.

In addition, with such a highly insulating glazing, the requisite cooling power of' fhe ro~frigerated display case would also be considerably lower.

There are various measures or combination of such measures that might be employed in order to improve the thermal insulation of a multiple sheet Insulating glass.

The first possibl' 'y is to increase the number of insulating intermediate spaces. This is however generally not practicable beyond a triple structure with glazings for the doors of refrigerated display cases, as the overall thickness of such doors should be as small as possible for constructional and weight reasons. Further possibilities for Improving thermal insulating Include filling the intermediate space or intermediate spaces with a gas having a lower thermal Qoautivity than alr, evacuating such Intermediate spaces and, applying Infra-.red reflecting, light O permeable coatings to the surface of' the glass &heets facing tho intemediate space or IntermediAte spaces.

Suich measure.% have for example been proposed in ,E-OS 2~4 4 390 to Improve the thermalinutono window panes for the building sector. Stich measures are also alroady known In glazings for cold storage, chambers.

(for example, of the typo described in DE-OS 26 44l $23, D-Q$ 2a8 42 0145 or SP-0OS 0 036 657). By means of the combination of the two latter measures# tho thermri, Insulation of a gluzing our be improved considerably, without the total sheot thickness notably exceeding the triple structlure previously mentioned with two air, spacer, of' 6 mm width, a coefficient of' thermal transmission k (k-value) ov approximately 2.11 W/m 2 k being obtained, A comparaible k-value of 2#2 14/n 2 k la obtained with a double structure with. an air space of 12 mm, In which the outer shoot h a s a light-perrncable, infra red.-reflecting COAting mnde o~f gold on the side facing the intermedliate

-LI-

space, which at the same time serves as a heating coating, in order to 91iminate the formation of condensation on the outer side of this sheet, In this context, the coefficient of thermal transmission k is the heat-f lux density, based on th e temperature difference of the spacel bordering t" glazing on both sides. Thus three factors must be taken into account in the Qoefficient of' thermal transmission-, The aspect of the glazin~g Itself and the aspects of the air layers adja'.:ent to tnQ warm and cold sides of the giazing in acecordance with the following formula k1 1i0-. R wherein; R the resistivity to hest of the glazing, acoefficients OT thermal transmission towards the outside or Inside (I) When quoting k- values, t h e vaiues for the ocfficients of thermal tran.mssion are standardised according to average: conditions for a vertical glazing In the building sector to Oea 23 W/M2 k anrd o. I W/M 2 k, All k-values given below relate to these standardised boundary conditions, It goes without that In pra~ctice the actual Values In the case of4 refri~erated display cases can dev1ite from this sliehtlty, Thus the coefficient of thermal transmission 0/1 b'tween the lzing and the surrounding room vill a de4pend AmOngst other things upon the display conditions and the air flows in the display room, The same appliers to the coeff1IOint of tOcriaa1. transmission towa.rda the inner apace of tho refrigerated display CaO0@41,4 The latter too Is amongst other thltvs slightly dependent on the dimensions of the refrigerated display case in question and also upon the degree of forced air circulation, which is always present, with these refrigerated display cases in order to render the temperature within the display case more uniform. In this connecti~on, it should however be borne In mind that, for the range of the low k-values of interest in this case below 2 W/m 2 k, the eff/ect of the adjacent air layers on the k-value is relntively small. The insualting effect in this range is essentially determined by the high resistivity to heat of the glazing, and therefore quoting th~e k-values under the standard conditions referred to represents an adequate Indication.

As already stated, the k-value of glazings for refrigerated display cases can be reduced considerablyj in particular by using a filler gas with a lowar thermal conductivity in combination with an irifra red-reflecting coating, compared with the values above Z W/m~kt which were obtained with the arrangements referred to. Thus for example for a double structure, 4 k-value of W/m 2 k is obtalnedt when the 12 mm-wide Intermediate space Is filled0 with argon and n light-permeable coating having an Infra-rei reflection capacity of 92% is applied to the s9urface of' the outer sheet facing the Intermediate space.

Tests have In addition shown that with a triple structure an excellent k..value of 1 W/m, k can be achieved# With this &tructure# tho two intermediate spaces of 6 mm width are filled with krypton, and a light..permeablo, qoating w0i~ith at) Infra-red reflection Oapacity Of' 94% is applied on to the side of the outer/inner* sheot facing the Intermedlato sae Sly means of glazings with such low k.-valuen, the ooling power required for a refrigorated dis'plaly case c An be reduce!d cons Iderably. Xn addition, the temperature of the outer sheet of such a highly insulating glazing is in most circumstances above the dew point temperature, so that the expensive heating of the outer sheet can be dispensed with. Whether this is the cae, depends of course on the relative air humidity in the display room and the inner temperatur'e of the refrigerated display case, As the relative air h~u~dity increases and the inner temperature of the refrigerated display case falls, lower k-values for the S~az.ing are necessary, if the heating of the outer sheet is to be dispensed with, For normal applications, the k-values achieved are nlready al equjate. Thus, for example, with a triple structure having a k-value of 1 W/m 2 k, with an inner temperature of' -20 0 C In the refrigerated oisplay case and an ambient temperature of 25 0 0, the outer sheet Is kept free of condensation up to a relative air humidity of Tests carried out with suhhighly insulating $lazings for refrigerated display cases have, however, shown an unexpected serious disadvantage in comparison with conventional glazings with k-values above 2 W/m k.

If the door of such a refrigerated display case. is opened In order to remove goods, an ice or water film with surface temperatures above 00?C is formed on the surface of the inner sheet o17 the glazing facing the cold ntorage chamnber as a reault, of contact WJI.'0 the ambient air.

This take-9 place In the samq way with Conventional glazings with k-values slightly above 2 W/m k as wtell as with the extremely highly Insulating glazIngs tested, Oiferencoas In the quantity deposited cannot, as expected, be detected, as in both oaaen the Inner sheet temperature, Is well below the dew point teMperature of t~ie katibient, air with the usual relative air humiditien, Once the, door Is c loned, the film produced, which signiflcantly impeden the V104-throught disappenrn once, again. This Qocor- i 4th conm~tlonaj l azlnpr with, k-.

-7- 2 values above 2 W/rn k and an opening time of' 10 seconds within approximately one minute, if the relative air humidity is at approximately 65%. In the case of the highly insulating glazings, this condensation period is considerably longer. The condensation period is increased by a factor of approximately 2.5, if a glazing with a k-value of 1 W/m 2 k is used, The observed increase in the condensation period Is a considerable disadvantage of such highly 'C'nsulating glazings in practice, because during this period an unimpeded view through the door to the goods an offer is no longer possible. Essentially, this period should be kept as short as possible, and condensation periods of longer than 1 minute are normally not accQeptable for these applications, The inventIon aims to make available a highly insulating multiple sheet insulating glass with which an unimpeded view-through is guaranteed once again as short a tim~e as possible after opening and reclosing of the cold storage chamber door, This problem is solved in accordance with the invention by the fact that In a multiple sheet lasutating glass Cor a cold st~rage chamber with forced air ciroulation and having a coefficieflt of thermal transmissnion of less than 2 W/m 2 k, preferably less than 1,6 W/m k, the outer surface of the Inner sheet of tho 61ass Is provided with an infra-red reflecting. coating, the thermal reflectivity of which in mnore than 50% in the wavelength range above approximately 4i pm.

The thermal veflootivity ot thi infra.-red reflecting. ooating, iv preferably Moro, than The lnfra-rod rofleoting 00ating May be -poadO Or doped tin oxide and/or doped indium, oxide.

In another embodiment of the Invention, the infrared reflecting coating is a metal coating made of copper or gold, which has a dielectric anti-r'eflectio~n coating on the side remote from the inner sheet, The dielectric anti-reflection coating may be made of metal oxide.

A The reduced ooneiensation time achieved by means of such a coating on the inner sheet of the multiple sheet insulating glass In the case of highly insulating glazings for cold storage chambers with forced air oirculation is an iistonishing result, Admittedly glazings are known, which divide colder from warmer space and which have an infra-r td reflection coating on the sheet surface facing the colder space, Thus in accordance with De-.05 28 33 2V4 the formation of ice during cold. nights on the outer surface of toughened automotive glo ings is reduced by such a coating, As already stated above and as the tests set out below confirm, the arrangement In accordance with the Invention f an infra-red reflecting coating on the outer sorface, of the Inner sheet of a highly thermal Insulating 00.1A storage chamber glazing can In contrast to this not directly produice reduced formation or ice, The sol.ution to the problem undeorlying the Invention can therefore not be taken frota this prior Patent.

In accordanoe with PE-.QS 28 42 045, a refrigerated display case glazing. Is improved with regard to ita thermal Insulation as a result of the arrangement of ant Infra4re refleoting Ooatinig on the outer surfacoe of the inner iheet, only if the refrigerated displaiy ca~o iq horizontally glazoed and no forood air oirculdtion is -9carried out. In contrast to this, for refrigerated display cases with forced air circulation, to which this invention relates exclusively, it is expressly emphasized that the arrangement of an infra-red reflecting coating on the outer surface of the inrer glass sheet has disadvantages compared with mul.tiple insulating glass units, in which infra-red reflecting coatings are arranged only on the sheet surface facing the intermediate space, DE-OS 28 42 045 thus provides a theory which leads directly away from the invention; this also applies to EP-OS 0 Q36 657, which also expressly recommends that the infra-rei reflecting coatings be arranged in such a way that they cannot solve th eproblem forming the basis of the present invention, namely on the sheet surfaces facing the intermediate space or one of the Intermediate spaces, Various materials can be used for the lightpermeable infra-4red reflecting coating on the outer surface of the inner sheet of the $lazing facing the cold ,storage chamber, the Inner space of the refri~- 8eration display coa.,e. In -pticua oe i n indium oxide coatings are suitable, such coatings, being oharaote-rised by a high degree of light permeability In onjunction with high infra-red reflection, and being mochanioally very Wstable. Also suitable are, for example# thin coatings made of the metals gold, copp'er and silver, in particular multiple coatingst in whic,h these metal oatings are embdded on both cides in Interfereoe, layers, in order to incrleasce thi light, permeability and also to improve the mechanical and ohOMI,,al reslistanae* In order that the Invention may be reAdily 3~i underrtoocit on embodiment therear will1 now be described In gre4ter* dotail with reference, Ot the Accompanying dvavina, the figure of whioh illustrates one examvtle of a Ohl -1 1 1 1 1 1 1 1 I I I I I &AM-Nowd multiple sheet insulating glass embodying the invention in section perpendicular to the plane of the sheets.

As is apparent from the, drawing, the multiple sheet insulating glass illustrated therein has an outer sheet ar, intermedia~e sheet 12 and an Inner sheet 14, eacQh of which is made of silica glass and has a thickness of 4I mm. Between the outer sheet 10 and the intermediate sheet 12 on the one hand, and between the intermediate sheet 12 und the inner sheet 14i on the other there are an outer, gas-filled Intermediate space 16 and an Inner gasfill, ed Intermediatl space 18. The two intermediate s Paoes 16, 16 are eaoh 6 mm wide and are filled, with krypton, On the surfaces of the outer sheet 10 and the Inner sheet 14 facing the respective intermediate spaces 16 and 18,1 there ave !lijht-pcrmeable Infra-red reflection coatingsq 20 and 22 having a thermal reflection oapaqity of 9M$ On the outer surface of the inner sheet 14 which, In usel faces the cold s5torage chamber, there Is a 0 fu.rther, light-permeable infra-red refleattng coating, 284 also having a thermal reflection capacity t, 5 whereby the infra-red reflection coatings 20, 2, P4#, in the embodiment shown are made of silver emrbedde'd U~ SnO, anti-retlection coatings.

The k-value of the multiple sheet insulating glans desoribed above aInd shown diagrammatically in the drawing Is 1 W/m 2 k.

In order to prove the way in which the Infra-red rerlecting coating 24 on tho no~r~ace of the inner sheet 111 facing the cold storage Ppace works I accordance with the invention) a comparative test was u..irioed ot.i on a front-glazed deep freeze display case. The deop: fleoze disfplay oane, had two window-like doors of identical dimons-ions,j one of which wa 5 glazed with a multiple sheet int-ulltinj; glans em~bodying the invention Is doesc(rited b- I L.1- above, with dimensions of 71 cm x 12? cm, The other door was glazed with a mktltiple sheet insulating glass having identical dimensions, but of a modified structure, in which the infra-red reflecting coatirw. was omitted from the surface of the inner sheet 14 facing the cold storage space 9 Otherwise, the comparative glazing had an identical structure to the embodiment of the invention described above, IQ With, the Inner temperature of the refrigerated display cas&e'at -210C and the ambient temperature at 250C and with relative air humidity of 75%, there was no formation of condensation on the Side of the outer sheet ftacing the atmosphere of either glazing. Both doors were then opened simultaneously, for 10 seQnds, This was carried out with relative air humidlity of the ambiient air at 60%. An lce film formed on that side )f the Inner sheets 14l of both glazlngs which Caced the Inner chamber of the refrigerated dlbplay oase, Cosdealyipeding, any viev through the Oo.rs., The Ivmpedence wasn -,,tbgtantintlly ijentlcal for both, glazing$, Following the -slmultaneous closure or both loor'sf the glaz.,ing with the ad~itionil Infrapq'ed reflocting oanting 24i In acceordanoe with the, Invention waFs 1ced up for a period of 60 siecondos, whilst this period wrls- 110 secoonds In the eaone of com~parative gaigwithout. art infra..red refleetion coating 24, This shown that the0 perilod the gtozing Is- covered over can be redui4ood by aprnroxirnately a factor of by the mreasure provided in accordance with the invention, which in comparison with, the teaching of DE-OS0 28 11 0115 could only be Adopted by, ovcroonilng ai preconception.

Claims

3. Mtltipl eet insulatIng glass, aooording to elain I~ or, t whoreirn the Inra-ed reflecting eoiting Is wade of doped tin oxide and/or Opec* Indiuma oxidei, 4, Rltiple aheet Insulating glassof ac(cordlng to claimp I ot 2, whoroin theo infri-rc-d reflecting coating Is a ~0mc'al ontin -Wade of silvor, orrioer or gold, which at lonj~s o~n thsc aide repmot" from the inner sheet htas a (ieectrio rintit.rflootion eIocting- ~xltile hee intdaingg~ha ordintg to claim 4, wherein the dielectric anti-reflection coating is made of metal oxide.
6. Multiple sheet insulating glass according to, any preceding claim wherein the said coefficient of thermal transmission is less than 1.6 W/m 2 k, 7, Multiple sheet insulating glass substantially as hereinbefore desovibod with reference to the accompanying drawing, 8, A glazed door for a cold storage chamber oomprisinq the mmltIp,'e sheet insulating glao3s according to any preced~ing claim. PAETF, this 9th day of July 1990, EtACHOLYAS 1u(TANCESELWLCITAFT Oiy its Patent Attorneyq PAVIF,$ 4 CObtLISON' 900107, lotlat. 040.CkWOUIk, too. 11