Space Heater Design in Ceramics Citation Welch, David Franklin (1943) Space Heater Design in Ceramics. Engineer's thesis, California Institute of Technology. doi:10.7907/ec69-we79. https://resolver.caltech.edu/CaltechTHESIS:03252025-184834663 Abstract No abstract. Item Type: Thesis (Engineer's thesis) Subject Keywords: (Engineering and Industrial Design) Degree Grantor: California Institute of Technology Division: Engineering and Applied Science Major Option: Engineering Thesis Availability: Public (worldwide access) Research Advisor(s): Unknown, Unknown Thesis Committee: Unknown, Unknown Defense Date: 1 January 1943 Record Number: CaltechTHESIS:03252025-184834663 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:03252025-184834663 DOI: 10.7907/ec69-we79 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 17091 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 31 Mar 2025 19:24 Last Modified: 31 Mar 2025 19:26 Thesis Files PDF - Final Version See Usage Policy. 13MB Repository Staff Only: item control page

$PACE HE.ATER DESIGN IN CERAI'-U CS Thesis by: David F• Welch In Parti al FUlfillment of the Requirements for the professional degree of Industrial Desi gner California Institute of Technology Pasadena, California 1 9 4 3 1. SUMNIARY OF THESIS A 10,000 B• t. u. ga s fired dome stic s p ace heater was desi gned in non-critica l ceramic n~ te r i a l a nd developed to t he p oint of production in conjunction with the Gladding MCBean co. The he ater v1as des i gned in several va r ia - tions to compete in a post-war ma rket as well as to meet an i mmediate need for small gas heating appliances in t he Los Angeles area. First a market s urvey wa s made to determine the size of the wartime repl a cement ma rket. The survey indicated t ha t 4,000 or more of t his type he ater could be sold annually in this a rea under pr esent restrictions. Fol lowing t he ma rket survey, studies were ma de of t he physi ologi cal and p s ycholo gical effects of heat, historical developments and pres ent trends in hea ting , sa fety codes and public he a lth, a nd f a ctors influencing th e c onsumer i n the purch a se of a ga s h ea ti ng a pp lianc e. Finally, a sp ecific t ype of l1 eat er which seemed best adapted to all consi dera tions wa s selected and a study made of its functiona l r e quireme nts. The comp leted de- si gn rep resents a synt hesis of i deas from various pha ses of the prel iminary rese arch modified by such practical a s pe cts as phys i c al cha racteristics of the ma terial and ma nufa cturi ng f a c i lities. 2. TABLE OF CONT'ENTS surrrrn.ary - - - - - - - - - - - - - - - - - - - - - - 1 Table of contents - - - - - - - - - - - - - - - - - - 2 Market Research summary - - - - - - - - - - - - - - - - - - - - 3 Demand - - - - - - - - - - - - - - - - - - - - - 3 competition - - - - - - - -8 Distribution Channels - -9 General Research Physiological and psychological Effects of Heat -11 Historical Developments in Heating - - - - - - - 16 ventilation - - - - - - - - - - - - - - - - - - -18 TY];) es of Sp ace Heaters - - - - - - - - - 19 safety Codes and Public Health Consumer Preferences - - - - - - - - - 22 - - - - - 24 Design The Problem - - - - - - - - - - - - - - - - - - - 26 Eleme:1ts of the Design - - - - - - - - - - - - - 28 Photographs Alternative Designs in ceramics J;.ppendix cost Analysis- - cost of Heating by Gas vs. Electricity - - - - -1 - -2 .Approximate aeights of combustion Products - - - -3 sources and Bibliography_ - - - - - - - - - - _ - 5 Acknowledgements __ - ___ - - - - - - - - - - -9 3. 111.ARKET RESEA..BCH COVERING THE LOS ANGELES AREA summary A study of the ret ai l ITB r l~e t for ga s burning domestic space heating units in this ar ea reveals the following: 1. A demand for a t le as t 12,000 s pace hea ters in t he fall and winter of 1943, which cannot be filled by dea lers' present stocks. 2. Roughly, 4,000 of these would fall into the small unvented bathroom heater class priced at from :}~3 .00 to $5.00. 3. There is no local competition for the market and little chance of any for the duration. 4. BY substituti ng non-strategic material for t he sheet metal and c a st iron in present models, a superior heater could easily be developed to fill in part the ma rket demands for the duration and compete with post-war units. All indications p oint to the inexpensive bathroom he a ter as being the most likely to comp ete in a post-war market, the simpl e st to ma nufacture, and having a minimum probable demand of 4,000 units p er year for the duration. Demand nuring t h e fall and winter of 1943 there will be a replacement market for ap:proxi::na tely 16 ,000 household space hea ting units in Los .Angeles area. The pres ent stock on ha nd is estimated to be between 2,000 and 4,000 units, which would le ave a market for at least 12t COO sp a ce h eaters under the present w. p. B. re- strictions in the fall and winter of 1943 . The w. p. B. in Washington has issued t wo orders which directly affect the s a les and manufa cture of space heating ap pli ances. The order L31 issued during March, 1942, was primarily a gas conservation measure restrict- ing the sales of all domestic gas he ating e qui pment to re pl a cements of condemned units of the s ame type and capacity. Order L79, issued July, 1942, prohibited the manufa cture of all domestic gas heating equi pment except upon speci a l re quests app roved by the board. Its purpose wa s to conserve critic a l labor a nd material. In .April, 1943, the w. p. B• rele a sed a cert a in amount of thin gauge sheet steel for a number of uses including the limited ma nufacture of space he a ting equi pment. shortly a fter this a speci al re qu est was ma de for t h e dev elopme nt of cooking stoves and heating units in c er amics for milit ary purposes. The bulletin mentions similar a pplic ations which ha ve p roved successful in Europe and encoura ges further research on ceramic heating units in this country. 5. Estima t e s of t he 1 94 3 ma r ke t ar e bas ed on t he f ollowing monthly s ales ma de under order 131 a s reported to t he s outhern Cali f ornia Ga s con:pany by its re gist ered dealers ·who account for 60?~ to 75% of the total volume of s ales in t h e Los .Angeles District. Peak sea son month sales ma de under W.P. B. order L-31 1942 sept ember 2 ,705 units October 3,042 units November 4,582 units Dec ember 2 ,140 units total 12, 469 uni ts Prior to order L-31 Il4I 2, 969 units 5,796 units 7,049 units 6 , 887 units total 2"2 ,701 units The above summaries repr e sent the nwnber of unit spa ce hea ters (vented and non-vented) sold by southern California Gas compa ny re gistered de a lers during the peak season from September to December. s unJ.In.er s a les a s r ep orted in 1942 amounted to a n average of 250 per month. simi lar reports a s of February 15, 1943~ of stock on hand indic a t e that only 740 sp a ce heaters are held in stock. Reluctance in decla ring full stocks mi _zht be partially responsible for such a low fi gure. BY using 740 as a ba se a nd a ssuming 260 uni ts h eld by other dealers not r egist ered with the Gas company and multi pl y ing by four we arrive at a liberal estima te of 4,000 space h eaters in stock February 15, 1943, in the 10s .Angel es area. 6. on the basis of sales from September - December in 1942, of 12,469 units as reported to the Gas company, the total unit sales for the area could be estimated at approximately 16,000 units. With the estimated available stock of 4,000 heaters on hand and no more having been manufactured since July 1942, summer sales of approximately 1,500 units could be neglected and the present stock would last only until the month of October 1943 leaving an unsatisfied demand for about 12,000 units for the rest of the season. Removal of the ;t. p. B. restriction 131 would greatly en- large the p otential market. A. possibility of relaxing restrictions on the use of natural ga s in this area was suggested if the present plan for dry storing natural gas in oil fields at Playa Del Rey proves successful. warehouses full of space heating units which mi ght be moved into the market before next season are quite unlikely. A satisfa ctory unit made from non-critical mat- erials by non-critical l abor is necessary to help fill the demands of the large repl acement market. Limited quantities of sheet metal will :p robably be released at intervals throughout the duration of the war to hea ter manufacturers in non-critical l a bor a reas. 7. This will relieve the short age to a cert ain extent but is quite unlikely to satisfy the replacement market alone in this area. Any satisfactory heater developed in a ceramie or substitute material would be enthusiastically supported by thew. p. B• and would have tremendous marketing possibilities. ceramics have always been the most satisfactory refractory material known. Tile stoves have been used successfully for domestic he ating in Europe for several hundred years. Recently stove and he a ter design in ceramics has been revived. Experiments have been made with glass stoves in this country, and several companies are manufacturing a tmospheric ga s burners pressed and slip cast in ceramic material. Developments in gas fired industrial furnaces have proven the value of burner desi gn in ceramics incorporating the principle of surface combustion. Resistance to corrosion and low coefficient of he a t conduction are properties essential to good burner design and are characteristic of ceramics. other physic al properties such as shock resistance and wei ght naturally limit its a pp lication and uses. Its advant ages must outwei gh its limit a tions in a particular ap plication for ceramics to comp ete successfully in a post war market. 8. comp etition 1ocal comp etition with ga s fired s pace h ea ter manufacturers does not exist. w. p . B ■ order 1 2 9 has prohibited t h e use of critic a l ma t er i al for t h e manuf acture of heating e qui pment in this ar ea which is also desi gnated as a critic a l l a bor zone . BY using non-critical ma t- eri a l and no a ddi t ional la bor, p r oduction could be st a rt ed on a new a ll c eramic h e e t e r which ·would help relieve a shorta ge in t hi s a re a . T~ere are ap prox i- mately ten he at er manuf acturers in . this area who are now either engaged in wa r p roduction or a re closed dov.m. These companies ma y be considered out of the field for t h e dur ation but will offer com11 eti tion for t h e p ost war ma r ke t. The w. p . B■ is p ermitting a few companies in the :Middle West to manuf acture l i mited numbers of domestic spa ce hea ti ng units to h elp a llevi ate the sho r t age. Dealers' stoc ks in t h is ar ea are now limit ed to h ea ters ma nuf actured by t hese coml) anies. These few ma nuf acturers, and possibly a few ce ramic compa nies wh o may deve l op ga s he at ers, will quite li ke ly be the only competition for t h e dur e. tion. s ev e r al ceramic conro a nies were s t arti ng to p r oduce atmosph er i c c e r amic ga s burners befor e order 179 wa s issued in July , 1942. There is no evi denc e of develo pme ntal work on all ceramic he t:i t ers 9. available although it is highly probably that the ceramic industry is doing some research work on the problem. The hee ting industry in general is investi- gating ceramic substitutions which will permit them to resun1e ma nufacturing. Distribution Channels The gas heating industry has always been made up of a number of comparatively small manufa cturers. This sim- plifies marketing and distribution problems as most transactions are direct orders from the retailer to the manufacturer. AS a general rule, local manufacturers have supplied a major portion of the local market. Dealers' stocks now contain a larger proportion of heaters from mid-western manufacturers because of manufacturing restrictions. Heaters are sold through a number of different outlets, some of which are: 1. Gas companies 2. Gas appliance dealers (registered and otherwise. Mail order houses 4. Heating and ventila ting comp nnies 5. Department stores 6. Furniture stores 10. 7. Ha rdware stores. Domestic sp ac e he a t er sa les appro ache s c an be cl as sifi ed int o sev er a l t yp es: 1. To interp r et cust omers' needs and sell a unit wh ic h be s t fits t h em 2. To meet a s pecified price range which t he cu stomer dema nds 3. To sell t he hea t er with the best mar gin of profit r t is ma inta ined t ha t any unit t h e s a l e sma n wi sh es to emplrn si z e c en be sold to t he e vera ge cus t omer who ha s no pr e-conceived i de a of a definite price he c a n pay . This i ncludes units of different c apa cit i es, appe arance s , effici encies, and rea sona ble p rice vc. ri a tions. Ma il order houses do a very l a r g e volume of business on t he price ba si s , with a sma ll bathroom heater in t he }3.00 price range having t h e gr eate st turnover. The ga s app liance de alers and gas compa nies are more interested in filling the customer's needs in the most s a tisfa ctory way possible. In all but the hi gh er priced department stores, the small 10,000 B• t. u. bathroom he a ter at from $3.00 to $5.00 were out- s elling all oth er models,. 11. GENERAL RESEARCH physiological and Psychological Effects of Heat Health and physical comfort are the two principal objectives of heating , ventilating, and air conditioning. The combustion of food within the human body re- leases heat energy which helps to maintain the natural organic functions of the body, build tissue, and provide work energy. Heat is released a t a rate which raises the body temperature of the normal human being to 98.lF. and provides energy. This temperature has been conditioned by ma n's envirorunent over n~ny generations and seems to be the tem1)8 rature a t which huma n organism functions most efficiently. The· temperature regulating system of t he body quickly r ea cts to excessive hee.t by or ening t he pores and a ctuatine; the swe a t gl ands or in the ca se of cold, c ontracting the pores and blood vessels near the surface to conserve heat. ivhen this adjustment is severe enough to become difficult, the body experiences a sensa tion of discomfort. conditioned res ponses can also cause discomfort when the temperature re gulating system responds to the si ght of an open window or other stimuli. In its present st age the metabolism of the sede nt ary human being is regulated to generate sufficient heat throu gh the metabolic process to '::ia intain a body temperature of 98.6 °F. 12. and dissipate heat to surroundings at t h e optimal rate ror human comfort when the enviornmental temper2ture is about 68.F. This tempera ture varies with people in dif- ferent climatic zones as well a s from winter to summer. Heat is dissipated from the body by means of three principles: 1. Radiation to cooler surroundings 2. convection 3. Evaporation For the average sedentary a dult, these transfers take place in the following app roximate percent ages: Ra diation 46% convection 30 7; Evaporation 24)~ Activity produces a ri s e in the katabolism and therefore in the amount of hea t which must be dissip uted. The pra ctical p roblem of heating amounts to the control of surrounding temp era ture conditions so tha t these three processes can function and he at can be dissipated at the normal rate for comfort. Heating is usually con- cerned with the adjustment of low temperature surroundings while air conditioning is usua lly concerned with the adjustment of hi gh temperature surrounding s, hum- 13. idity control, and air purific at ion. Flexibility in regard to the relative umount of he et dissi pa ted by radiation, convection, and evapora tion is p ossible. If the deviations are not too extreme and the tot al amount of he et dissipated is sufficie nt, comforta ble conditions are still ma intained. A simp le c a se v10uld be lowering the moisture content on a hot, humid day to p ermit more ra pid cooling through evaporation when it is not possible to lose heat through r ad iation because t h e temp era ture gradient between the body and the surroundings is in the wrong direction. some of t he princi pa l environmental f a ctors affecting health and comf ort a re: 1. Dust content of the aid 2. Temperature of the air 3. Humi dity 4. Motion 5. Pressure 6. Temperature of surroundings 7. Distribution of heat s. Odors 9. Visible ligh t 10. sound Human occupancy al t ers the air in a room by 14. 1. Using up oxygen 2. Increasing the C 0 1 content 3. Increasing the humidity 4. Increasing t he temper a ture 5. Introducting products of organic decomposition DiscoLlfort due to breathing stale air has been proven by psychological experiments to be far less import ant than that due to interference wi th the normal evaporation from the skin. The carbon dioxide content of the air c an be increas ed to 35b without causing any noticeable effect upon the occupants. The average C o~content of outside a ir is only 0.03% while that in the average occup ied room is 0.1%•* A much smaller relative change in the moisture content of the a ir will cause marked discomfort. The ~revention of excessive he &t loss from the body which i s the objective of he ating may be accomplished by: 1. controlling the air temperature 2. controlling the temperature of surrounding objects 3. Raising humidity 4. Decreasing air velocities * F. A• Moss; "Your Mind in A.ctionn r-; l v• vari a tion of these factors must again be within certain limits f or comfort. The follO'lning are app roxi- mate com.fort r a nges for t he fully clothed sedentary adult: Temperature air and surroundings 65 - 70°F. Relative humidity 507b - 60% Air velocity 15 - 30 feet per minute BY simula ti ng conditions in nature under which we feel most comfortable and alert, we can set up an objective for heating and ventilating . In the cool, clea r air of the mountains or desert, receivi ng ra diant heat from the sun a nd earth, and with a sli ght breeze from the front, we have very close to i des l comf ort conditions. For long p eriod heating t hese conditions would suggest a r adiant source a round the ceiling line of a room which would r ad iate hea t to the floor and sur rounding objects from as l ar ge a surfa ce a s p ossible. The ven- tilating requireme nts would be a supply of fresh, clean air circulating with a velocity of from 15 to 30 feet per minute. It is logical that ment a l efficiency should be highest when no bodily sensations tend to distract from the thinking p rocess. This condi ti on ca n be app roached by l G. re gula ting environr;:er: t t o c onc.i tions for :·:1sxi mum comfort e nd by completely relaxing t i1 e body. some psycho- logic a l ex;e riments on subj ects in c ontrolle d at mospheres h e ve suc;gested t ha t teLlI) er ~ture huni di t y , and the c 2r bon dioxi de content of t he a ir c an be r a ised to quite h i ~h values before any decrea s e in u ental efficiency is noticed under stimul a ted l es rning. Pr a ctical results have prov e n the opposite, that approxima tely 605b more errors a re L12d e on a hot summer day t ha n on an average day. Historical Devel opme nts in Heat i ng The first aJ:p lic ntio n of ,_, rtificie.l heat wa s :prob a bly a fire of dry sticks and le cves in a cav e or natura l shelter. ~ith the a dv ent of t ents and huts e n opening wa s left in th e r oof for s1i1oke to es cap e. :i?or k :ble stoves and cha rcoal br a ziers without J rovisi on for venting we re used l ut er by t h e Romans . Eee ting by hot vm t e r ·.,a s used. firs t in t Le Homan ba t h s b y l'tmning Da t er t t rough bra ss 9i pes with wood fires un derneath. Fire pl a c e s \Je re us ed f or many yeEirs v:i thout ~) rovision for dr, ft or venting until about the 'fwe lfth Century, when t h e chimney wa s introduced. The fire pl a ce has be en ret e ine d mostly because of its ps ychol ogical value as it has an ef ficiency o f only t en or fifteen p ercent acting as a r ad i a nt source. stoves were used for the 17. first time about 1490 in Alsace but did not come into general use for almost three hundred ye c1 rs. Iviost of the earthenware stoves built in Europe v 11ere made in the seventeenth and Ei ghteenth Centuries. Many were constructed of rather elaborately designed tile blocks cemented together to form and cylindrical stoves. highly decorative rectangular Most of these stoves were sup- ported by iron legs and occupied a rather large space either in the corner or near the wall so they could be easily vented. cool green and grey glazes were pre- dominant in the ordinary stoves while the elaborate porcelain stoves were often delicately hand decorated. These stoves were slow to heat up and were only satisfactory for heeting over long periods. In 1744, Benja- min Franklin invented a cast iron open he a ter which projected out from the chimney and r a diated heat into the room from all sides. He also made the first attempt to construct a hot air furnace which would supply pure heated air to the room. steam heat was first proposed in 1750, and a hot water heating system was used in Paris to heat a hot-house about twenty years later. The sheet iron stove was developed in the early Nineteenth century. ,1utomatic damper control was intro- duced later and in 1845 a cylindrical stove lined with fire clay was constructed. About the same time the base 18. burner stove into which coal was fed from a ma gazine above was invented. came out. In 1875, the first oil stoves BY 1890, ga s stoves were being developed. Electrical heating was the next r adical step forward and is still in its early stages. Solar heating has been experimented with but no practical installments have been ma de. Radiant heating has attracted a great deal of attention lately and is felt to offer a solution to many former heating problems. It is based on the theory of heating surrounding objects to a temperature sufficiently hi gh to prevent excessive heat loss from the body through r a diation. Lower air temperatures are possible which it is thought will reduce he a ting costs. :rn any c a se, this trend approaches conditions in nature more closely than any previous attempts in heating and will undoubtedly be developed more thoroughly after the war. Induction heating through the use of ultra high frequency current may also have possible applications. Ventilation The history of ventilation parallels that of heating, although very little thought was g iven to it before the Nineteenth century. The Egyptians constructed ventila- tion shafts in their pyramids and the Romans left openings in t heir roofs for the purpose of ventil etion and 19. temperature control but very little serious at tention was given to the sub je ct until it came up in connection with mi ne opera tion. In 1843, a study of hospi t al ven- tilation re quirements wa s ma de by the French governn1ent. sir ttwnphrey Davy in 186 1 me de t he first att empt to introduce the need for proper ventil ation to t h e English parliament. Earliest attempts a t securing prop er ven- tilation in the United states were in re ga rd to public assembly halls. Blower systems later supp lanted nat- ural ventilation and ai r condi tioning is the l a test advancement in the field. Types of space Heaters The general trend in domestic heating has been toward centralized he a ting units. In this pa rticular climate, floor furnaces have proven very satisfactory. These units are more economi cal to install and have higher overall heating efficiencies a s there are no conduit losses to contend vnth. supplementary heating during abnormally cold spe lls or in isolated rooms is often provided by port able s pa ce hea ting equipment. Space hea ters may be classified a s follows : Gas - vented and non-vented circ ul ating r a di ant 20. combina tion Electric circul:3. ting r a diant combination stoves (oil, wood and ch&rcoal) circula ting radiant c ombination supp lement ary s pa ce he ating by gas and electricity has many a dvantag es over stove heating which is used only in rural e reas. Electrj_c heating is undoubtedly the most a dvant ag eous from the health standpoint. Its two serious handicaps are its cost and its limited heating cap a city. Electric heating per 3. T. u. of output costs 19 times that of gas at average rates for the meditu.71 income domestic consumer. * The "'.JB. ximum. output of an electric heater connected to a household circuit desi gned to c arry 15 Bill!)eres of current would be ob out 1,500 watts whi ch is e qui valent in heat output to a gas heater of half the capacity of the small 10,000 B. T• u. bathroom he ater. A special cord would be required to handle the current and initial costs on electric he a ters are also higher than those for gas units. * see Appendix 21. Gas he a ters of the circ ul ating type are t h e fastest and most efficient s pace heaters. They heat the air and set up natural convection currents which distribute the heat throu ghout the room. Radiant heaters are superior for rapid heating of }) ersons or objects which are near the r adiant source and exposed to its direct rays. Gas hea ters come in both vented and non-vented types up to the capa cities of 40,000 B• t. u.s hour. per Above that ca~) aci ty t he y are all vented he aters with the l a r gest heaters r ated a t about 60,000 B• t. u.s per hour. A 10,000 - 12,000 B. t. u. heater is designed to maintain a room 10 ft. by 10 ft. at a comf ort able temp era ture under average vvi nter conditions. This size heater is used primarily to he ,: :;t bathrooms and bedrooms for short :p eriods in t he morning a nd evening . are u sually white or cre am . colors Prices on these units r ange from ) 3 .00 to $5.00 and they have a l a r ge turnover in sales. A 20,000 B• t. u. heater selling a t from $14.00 to $18.00 will heat a room about 12 ft. by 15 ft. and is t he next best seller. The large r capacity heaters are usually finished in dark brown and imitation wood :pa tterns to blend with the furniture. Wall heaters re quire s:pecial inst a lla tions and the imitation log heaters are novel but very inefficient. 22. safety Codes and public Health Health and safety codes have been set up with the purpose of 9rotecting the public. These codes vary from state to state and even from community to community. In regard to gas appliances, the Health and safety code for the st ate of California st a tes that every gas-fired appliance, except kitchen gas ranges, which is desi gned to be a vented appliance shall be provided with a vent pipe or flue leading to outer air. It also states that every gas vent and appli- ance shall be kept in good repair. Pasadena building codes re quire that every ga s heater with a capacity of 40,000 B. t. u. s or over and every bathroom heater regardless of size be vented as well as provided with intake air. carbon 1aonoxide, a product of incomplete combustion, given off from defective gas appliances may prove fatal in an hour at concentrations of 0.4%. Health author- ities have set 0.01% a s the maximum concentr ation of carbon :aionoxide gas which will not give rise to a ny symptoms. small quantities of water vapor and carbon dioxide, the :p rinci pa l p roducts of combustion, are not considered injurious in themselves but do increase the toxic effects of any c arbon monoxide which mi ght be 23. present. In t h e early 1920s, the Ohio stete Board of Health ma de t he most comp rehensive survey of as phyxiation by carbon reonoxide wh ich ha s been published. u ore than ha lf of the c as es were c au se d by defective domestic appliances. The wo rst menace was the ga s stove left burning in p oor homes to heat the room during cold winter nights. c oa l and coke stoves, ho t wa ter hea ters and ba t h room hea ters we re responsible in the order listed for ot her case s of a sphyxi a tion. Unvented ga s h eaters of t he r a di ant or circulating types were considered e qually dangerous when used for continuous heating . From the standpoint of health and s af ety providing every heating appliance with a vent and supply of inta ke air is very desirable but at the same time much of the danger involved in using unvented heD ters can be avoided by keeping t h e a pp liance in good operating condition. The A,mer ic an Ga s Associ a tion sp onsored by the ga s heating industries for the promotion of ga s h ea ting, maintains a series of r esea rch and testing l aboratories. A numbe r of s afety and effici ency r equirements have been set up wh ich must be met by a ny hea ter submi tted to the laboratory before t h e app liance receives t he A.G. A. stamp of app roval. These re quirements for A• G· A• approval serve to protect the consumer and at the same time promote t h e use of ga s appliances by helping to overcome fear and pr ejudice against gas as a fuel for domes tic he ating. consumer Preferences The vali dity of a selective consumer survey, even though it covered 10,000 residences, would not be great a s this number represents only two p er cent of the 500,000 middle income single dwellings in this area. i'far Production Board re strictions and many othe r factors affecting t h e normal consumer ma rket make it almost i mp ossible to conduct a vali d survey during t his period. It wa s felt that by interviewing people dir- ectly connect ed vvith the field of selling and manufecturing ga s hea ting units that a much more valid survey of possible desi gn im~rovements could be made. Informa tion on consume r pref erences was ob t ained from s alesmen in a va riety of r et a il outlets and from discussions wi th potenti a l consumers. This materi al in- dicated the best selling he aters were found to be the inexpensive ba t hr oom he oter in white e nd cream enamel and the 20,000 B. t. u. circulating or combi nation r adi e nt circ ulating he 2ter in dark browns. Va ri a tion in t he desi gn of several h ec ters of the same price 25. r ange a nd c a pacities vva s fo und to be a very va luable sales f a ctor a s the consumer is given an opportunity to choo s e between several he a ters inste ad of being forced to t ake the only one s hown him . .As sma ll and compa ct a he a ter a s p ossible wa s also found to be desirable from t he cons umer's point of view. Na turally , pr ice is a lso one of t h e mo st imp orta nt f a ctors. 26. DESIGN The p ro blem The desi gn of a sma ll s pace h eat er wa s chos en a s the practic a l problem. This choi ce Wei s sugge sted by a s tud y of the ga s a pp li ance mar ke t under wartime restrictions whi ch indic at ed a p otential demand for approxima tely 4,000 low capa city s pace he a ting units per yea r in t h e Los Angeles a rea . ceramic material wa s chosen a s a substitute for critic a l meta ls because of its non-priority st atus, its res istance to corrosion, and its qualities a s a r efr a ctory ma teri al. Ga s wa s s elected a s a fuel because of i ts low relative cost, i ts c l eanline ss, and its excellent combustion cha racteristics. A 10,000 B. t. u. unve nted hea ter seemed best adapted to all pr a ctic a l co nsidera tions. The volume of ? O- tenti a l sales, comp eti ti on in the post-wa r :-,rn r ket, the limit a ti ons of cerarai c ma t eri a l, operating efficiencies, a nd ea se of production were a ll f a ctors affe cti ng t he choice. The fun ctions of this t yp e h eate r we r e ana li zed and t hen a survey of e xist ing heaters de s i gned in sheet metal wa s studied. A substi- t ution of ceramic mat eria l for shee t me tal na t urally 27. means more c areful handling would be necessary to avoid breakage. A permanent gas connection as advo- cated by the ga s companies would gr eatly reduce the danger of the heater being knocked over on a tile or hardwood floor and broken. The glazed surface will be ea sy to keep cle an and will not cha nge color or fade. The performance of the ceramic burner s hould be superior to tha t of a cast iron burner a fter several years of usa ge. The p•o rts in ordinary c ast iron burners are rapidly corroded a nd clogged wh en tr aces of sulphur are present in the ga s wh ile t ho se in a ceramic burner are not affected. Improp er combustion with its very dangerous effects is o ften caused by a badly corroded burner. The unvented 10,000 B. t. u. he a ter will warm a room approximately 10' x 10' under averag e ea stern winter conditions. They must heat t h e space . s a fely, rapidly, and uniformly. In the Los Ange les a rea, these heaters are u sually used a s s upplement a ry heating and only for brief periods in the morning or evening. A rubber con- necting hose is used in most c a ses to s upp ly gas from the outlet des pite protests from the ga s company. The hea t e rs a re ii l a ced close to t h e wall a nd c e. n be move d 28. to outlets in other rooms a s supplement ary hea ting units wh en necessa ry. A low initial cost permits t he purcha se of s everal unit s t o avoid the trouble of moving t he hea ters from r oom to room. A c a se or grill is necessary to prevent curt a ins, clo th ing , or any oth er ma terial fr om c_oming in cont act vd th the ga s flame. suffici ent a ir s upply must a lso be p r ovided to p ermit c ompl e te combustion. Elements of t h e Design Ba sic elements of t hi s t yp e he ater a re the orifice, the burner, the c a se, a nd t h e ho s e connection. These ele- me nt s must each be designed to fulfil its sp ecific requirements a nd t hen be coordina ted with t h e others to fulfil t h e functi onal re quireme nts of t he h ea ter. After t h ese conditions are me t, attention may be concentrated on app earance and s a les appeal. The orifice di ameter and the line pressure are main f a ctors wh ich determine the amount of ga s flo wing into the burner or t h e maximum capacity of the he a ter. A slope of 45°t ap ering from t he inside diameter of the ga s l ine to the neck of t h e orifice pr events excessive t ur bulence through t h e ori f ice :. . The orifice must be securely loc a ted a t a ce r tain dist ance from t he burner 29. throat to insure p ro per mixing . The primary a ir may be re gul ated if necess ary by a dding an a djustable shutter. A meta l which does not corrode should be used for the orifice. Brass has been found to be a satisfa ct ory ma teri al in this applic ation. The burner performs t he most i mp ortant function in the he ater. The ga s and air combina tion inject ed into the burner is 1t1ixed in the t hroat and forced out t hrough a nun1ber of small ports on t h e top of the burner where it is i gnited and burned in t he pr e s ence of secondary a ir. Raise d ports are des i r able to p ermi t an a d- equ ate s ec ond ary a ir supply. These l) orts s h ould be close enou,gh togeth er to enab le t h e fla rae to propagate ea sily when li ghting . Tem,e r atures should be compar- atively low around the mixing throat to prevent prei gnition. * A compar i son of c ast iron a nd ceramics for use in burner desi gn shows t h e f ollowing : 1. corrosion resist ance of ceramics far sup erior to c ast iron. 2. Heat conductivity of ceramics compa ratively low. 3. p ropos ed ceramic body not a critical ma terial. 4. c erami cs more fr ag ile and porous than c a st iron. * American Gas .Association; "Combustion" 30. The bo dy of t he hea ter functions a s a protective enclosure for the fla me, as a low tempera ture r odiating surface and a s a circula tion directive. The c a se or body s hould be sturdy, ea sily cleaned and, have a low center of gr avity. rt should be reasona bly li ght and provide some r:::e ons for c a rrying . An excess of seconda ry air should be 0dmitted from the bottom and circ ulat i ng openings shou ld f a ce forwa rd as a safety means to prevent t h e cha rring of curtains or dr ap es. The top wh ich will be t h e hot t est :p ortion should be sli ghtly furt her away from t h e wa ll a nd t h e le g s s hould be sufficiently h i gh to p revent excessive h eating of the floor. A hole must be :p rovided for lighting a nd scratching surface would also be convenient. Provis- ion must be ma de for securely a nd accura tely loc ating the burner t h roat with resp ect to t h e orifice. The hose connection should not have a valve. This makes it necessary to regulate the ,heater ,_, from the wall outlet valve which is the saf'er >practice in any case. A connection which would permit either a hose attachment or a pipe joint would be advantageous. In any case, it should be close to the body of the heater and fastened so a s to distribute any stress ove r as larg e a surfa ce os possible. 31. variations in a, pearance may be easily a ccomp lished to stimuls te s ales and yet c ause only sligh t V3riation in pro duction uethods. BY using different cutting templates t i1e sizes, spacing , and arrangement of the circu l ation vents in the c as e may be varied. colored g l a ze s will b e p ossi ble over a speci a l cer amic body but t he ma rk e t survey i nd ic a tes t h at cre am a nd white are t h e t viO :aos t popul a r colors for this type of h en ter. A rough, dork colored surface would t h eoret- ic a lly a ct a s a be tter r a di a ting surface but pr a ctically t her e is very little difference. These vuriations in desi gn will give t h e c ustomer t h e opportunity of making his own s c:lection and are c onsidered from the sales p oint of view a very desirable asset for any line of go ods. The Heater The Models The Molds The Molds and Finished Products The Assembly Alternative Designs in ceramics - ceramic case Circulation vents -- - Sheet Metal Heat Transfer surfaces --- vent Radiants ceramic Baffle Burner Down Draft Diverter center section A vented combination radiant-circulating heater utilizing a minimum of sheet metal. BY the use or sheet metal only in the most important heat transfer surfaces, efficiences comparable to those or all metal units can be attained. A Vented combination Radiant-circulating Heater The entire heater is designed in ceramics with the curvature providing low temperature radiating surfaces exposed to all parts or the room and acting as supports for the heater. Products of combustion pass up through the hood, are then diverted through the side wings and finally out or the vent. I ) f ceramic Reflector Wire Upri ght sectional Views Horizontal An electric heater using metal only in the switch and as contacts tor the carbon Glo-bar heating unit. The heater may be used in the upright or in the horizontal position depending on the heat distribution desired. A PPE N DIX 1. COST ANALYSIS Lar ge s c a le p roduction does not offer the percentage reduction in manufa cturing costs in t he ceramic industry that it does in most other fields. The cost of ma ter i a ls is very small in comparison to labor cost, firin g expenses, and rejection losses. Round corners, strengt hening ribs, a nd other factors in the desi gn can subst antially reduc e re jection losses. s imple molds nnd a minimum o f trimmi ng or finis h ing will reduce l a bo r costs. Ba sed on t h e production of several thousand units, the ap proximate manufa cturing costs p er heater are a s follows: Case $1.50 Burner .35 Hose connection .15 Orifice .10 Assembly .25 Total $2.35 2. comparison of the cos t of hea ting by ga s with the co st of h es ting by electri city for dome stic consumer in t he middle inc ome gr oup . Gas 1 B. t. u. of he at energy costs 8 •~~~g = 0.000000536 or 53.6 x 10- doll ars e j 0.60 per 1000 cu. ft. of nat ur a l g as with a hea ting value of approxima tely 1120 B. t. u. per cubic ft. Electricity 1 B• t. u. of he a t ene r gy costs 0.000292 x 0.0 35 = ;j;0.0000102 or 1020 x 10- 8 dollars © $ .035 per KW. Hr. 1 B• t. u.: 0.000 2 92 Kw . Hr. ,tt $0.015 p er KW. Hr. 1 B. t. u he at energy costs 0.000292 X 0.015: -0 -o 438 x 10 or 438 x 10 dollars 1020 x 10 . Hea tin g by electr i city is "5°3: 6 10"- or 19 -8 : X 8 times as expensive a s hea ting by ga s for the average domestic consumer in t he middle income group. At a sp ec ie l rate of $ 0.015 p er KW. hour, electricity is still ei ght times as expensive as gas per B. t, u~ of heat energy at the average rate for a small domestic consumer. 3. The a ppro xi ma te we i gh t of flue p rodu cts pe r of h ea t energy r el ea sed B■ t. u. during comp lete combust ion of natur a l ga s with a me thane c ontent of 85% are estimated a s f ollows: Assuming t he principa l constituent :methane to have a heating value close to t he hea ting value of na tura l gas of 1120 B ■ t. u. per cubic foot. 0.00004 C H1 = 202. K .,,_ Y= 0.00011 0.0000875 C O2. 2 H 2. 0 'I 'f 36 /6 c Hr weigh s 0.0447 # 0.0447 = 0.00004 17 of me t ha ne :per B.t.u. of heating 1 cubic ft. of 1120 va lue. Let x = # C 02. produced p er 0.00004 # of C H1/ 0.0 0004 16 : X 44- x : 0.00011 # C 0~ Le t Y = ll~ H~O pr od uce d 0.00004 16 - Y ~ Y = 0 .00011 #'I Hi_ 0 ,. •. A 10, 000 B. t. u. l1eat e r VJ ill produce app roximately 1.1 # c O2. per hr. 0 . 8 75 # H ~0 per hr. A.bout .0738 /I of C 0:1. are exhaled by the average person in one ho ur. In still a ir a t 68°F. a bout 0.095 # H~0 per hour a re exh aled and eva por ated by the average man's body. 4. This vvould indic a te t hat a 10,000 B. t. u. unvented he a ter gives off C O.t at a r a te equiva lent to 15 p ersons and H ~ O vapor equiva lent to nine persons. Twelve sedent a ry persons would give off approximately 4t800 B• t. u. of hea t ener gy p er hour as compared with t he 10,000 rele a s ed by t he ga s he ater. 5. APPENDIX sources of Informa tion a nd .Bibliography * used in Mar lce t Research section ** *** used in General Research section used in Desi gn section p ersonal co nt acts southern California Ga s company Iv1r. * *** H· V. Davis - Personnel Uanager I nst itu te of Ga s Heoting Industries* ** Mr. F• suf fron *** .tl.m.erican Ga s Association* Mr. F• A.llen * Los Angeles Examiner ** :Mr. N. Dover - Ma rket Research Bureau Los Angeles Chamber of cormnerce * Mr. G. Ma rion - Ma rket Research Bureau oc ci d enta l college ** Dr. G. Br igho use - Psyc~o logy Dep artment Pa s adena Board of Health ** Mr. J. Art hu r - Health Officer *** 6. ~I dea l Heati ng corpor a t ion *** Mr. E. s l ater *** Gem c l ay Fo r mi ng co. Mr . L• Munchh of Gl adding McBean e nd co. Mr. p . Tho rnton Mr. p . Porter r.1;r . R· Evans Pa s a dena Dep artment of Building codes ** Ga s AP ? li a nce s a lesmen int erviewed at: sea r s Roebuc k a n d Company (Pa s cde na a nd Los Ang eles) F . c. Na s h & co. Pa sadena Hardwa re s tore Lea de r Fu r ni t ure c o . Bul l oc k 's The May co . J . w. Robinson Ba r ker Bro th ers Benedic t a nd Gingrich Ga s App li ances * ** c orre s pond e nce corresponde nce wa s c a rr ie d on and c a t alog s or bulletins we r e obt a ined f rom 23 s pa ce he a ter ma nufa cturers and a sso c i ations * ** *** 7. Bibliogr aphy Health and Environment Hill &. Campbell You r Mind i n Action Moss, F. A• I nc re asing P ers ona l Effi c i e ncy Laird, D. A • Hea lth a nd Sa fet y Codes s tate of Ca li f ornia, 194 2 Car bon Mono xide - A Domestic Hazard .Americ an Ivledic a l .Association, July 6, 19 4 0 Prev en t ati v e Medicine and Hygiene Hos eman Hea ting , Ven t i l a ti ng and Air Conditioning Fund ament als Severns, w. H. Air condit io ni ng J enni n gs &. Lewis Air Conditioning in summer ar..d ·.vinter Holmes, R. E. Hea ti ng , vent i l a ti ng an d Lir c ond i ti oning Guide (18th edition) Th e 1\.meric an s oc i et y of' Heating and v e nt i l a ting Eng ine ers Hea t p ower Engineering (Part III) Ba rnard, Ellenwo od &. Hirshfeld Ra diant Hea ting Arc hitectur al Forum, J a nua ry, 1939 c ombu s tion - Indust ri al s eries .Ame ric an Ga s As soci a tion Approv a l Re qu i r eme nts for Gas Space Hea ters Americ an G&s As soc i a tion, 1943 8. Desi gn of Ga s Durners for Dome stic Use u. s. Bureau of standa rds, Circular 394, July 10, 1931 Ind ustri a l Furnaces Trinl{ 9. I wish to thank the following faculty members of the Industrial Desi gn section at the California Institute of Technology for their cooperation and guidance in t he compilation of this thesis: Mr. Antonin Heythum Mr. J . Paul Youtz Dr. Gilbert Bri ghouse Mr. Nathaniel Wilcox Mr. Beverly Morant