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One Flash Tank Is Recommended for System Since doiler pressure in CH't plant it only l^S psig, he is right in saying one flash tank and one heat exchanger is the most economical heat-sover sys tem lor his plant The system proposed for him was undoubtedly designed (or o high-pressure plant Sketch above shows a system that I believe will suit his needs best Piping used should be larger than lor a highpressure system, in order to get oil Rash steam possible from blowdown woter. About $0% ol heal in blowdown woter will be extracted from flashed steam while most ol remaining heat will be given up to feedwater makeup through'heat exchanger. Flashed steam may be piped to heater steam inlet, os shown, or it may be used for process or plant besting if present exhaust steam fills demand for healing* feedwater. Leave exact piping sizes to the design engineer. Arthur Belton Montreal, Canada One Tank and UquItMo-LIquId Heat Exchanger Uss or one flash tank and a liquid-loliquid heal exchanger is most eco nomical in CU't case. As makeup and blowdown are approximately the same, feedwater will be heated to 202.4 F provided blowdown is cooled to o tem perature ol 222.4 F. Less heot-transler surlace will be re quired to heal feedwater to 202.4 F il blowdown inlet is at 3 psig rather than atmospheric pressure. Incidentally, liquid-to-Hquid heat transfer requires less area than iteam-to-liquid, and vol ume handled is far less than il the blowdown is noi allowed to flash. Actu ally, il sufficient hcat-exehonger area is provided in either case, fuel saving will be the same. II flash tank No. 2 is eliminated, care must be taken to prevent blowdown liquid at 3 psig from flashing at entry to heat exchanger. It will not if friction loss through exchanger is over 3 pi. Pressure can be maintained in exchan ger by throttling or by Installing a short riser in outlet. Outlet pressure can be less than 3 p* as blowdown has been cooled at this point. Assuming a boiler efficiency of 75% and coal at 14,000 Rlu per lb, actual savings are easily worked out. Flashed steam to the deaerator saves 6) tons of coal per year. Cooling blowdown from flash tank No. 1 to 80 F (whether flash tank No. 2 is used or not) saves 49 tons of coal per year. As a matter ol in terest, latent heat in steam flashed from No. 2 tank amounts to only 3.6 tons ol coal per year. W L Covan Ontario, Canada Outlines Economic Study DtronE CH ean state positively cost of extra flash lank is unwamh' he must analyze the problem thas Determine enthalpy of water I steam-to-Uquid heat exchanger ordinary heat-balance methods sod culate efficiency of both exchu^t Then find enthalpy of water liquid-to-iiquid heat exchanger wb flash tank No. 2 it omitted. Differea' between these two values givesi satoas! of heat that must be added1 elsewhsr in cycle. Multiplying this result monetary value ol one Btu in (eedwst and number ol operating days s y< yields the extra annual eost of single-flash-tank system. Extra annual eost is then eom| with annual cost ol second flssb taking into account amount ol w depreciation, maintenance. This " parison quickly shows the most di able economic system. Addition ol second flash tank exchanger increases heat-lraoslei lace and efficiency ol blowdown if CH will find extent and eftekaey, heat-transfer surface dependent oa oua factors, some ol which are: over-all coefficient ol heat transmit (2) cost of a Btu (3) length ol t the surface is used during 1 Analyzing the blowdown systemi pletely and plotting the results* ^ loins a curve like the above. TW** greater saving as heot-transler s ( ihcreasea up to o certain P0 creasing surlace beyond this P creases saving. Above method e*0 termine system closest to ms**0 Ing. Tyler C Hicks Next York, N- 116 (7151 POWER Novahw\ EVERDUR CONDUIT protects wiringin nation's biggest under-water tunnel In new york's new 77 million dollar BrooklynBattery vehicular tunnel, one and three-quarter miles of Everdur* Conduit will carry traffic light and control cables, telephone and other commu nication lines. Both RC and EMT are being used in sites from W to 4". Control boxes will be located every 250 feet ' along this 9,117 foot four-lane sub-marine bouleVflfd. These boxes arc likewise being fabricated from Everdur Copper-Silicon Alloys. No stranger to long-term service under extremely corrosive conditions, Everdur Conduit has Performed impressively on the Delaware River r*dge since 1935, and in Pennsylvania Turnpike funnels since 1940. Its long life in refineries, sewplants and chemical works are good reasons 0r its use under New York Harbor. Everdur Conduit possesses high strength, is Don*iagnetic, workable and weldable. It is avail EPW|r , u NovomW 1948 able in two wall thicknesses: rigid conduit (RC) in nominal sizes from V4" to 4" inclusive; and the thinner walled electrical metallic tubing (EMT) in nominal sizes %" to 2" inclusive. Complete lines of fittings ... connectors, couplings, outlet boxes, etc___are available in Everdur Alloys from leading manufacturers. n**.u..ri.oo. "THE NATIONAL GUARD DIFINDS AMIRICA-J0IN NOW!" idA cwtoab ELECTRICAL CONDUIT THE AMERICAN BRASS COMPANY General Offices: Woteibury 89, Connecticut Subsidiary aj Anaconda Capper Mining Company . /ft Canodst ANACONDA AttlXICAM BlAAl LTD. Nw Tbrftftf*, Owl. 17