Part 11 (2/2)
SPECIFIC HEAT OF WATER AT VARIOUS TEMPERATURES
+----------------------+--------------------------------+ | MARKS AND DAVIS | PEABODY | | From Values of | Fronault | +-----------+----------+---------------------+----------+ |Temperature| Specific | Temperature | Specific | +-----------+ Heat +----------+----------+ Heat | | Degrees | | Degrees | Degrees | | |Fahrenheit | |Centigrade|Fahrenheit| | +-----------+----------+----------+----------+----------+ | 30 | 10098 | 0 | 32 | 10094 | | 40 | 10045 | 5 | 41 | 10053 | | 50 | 10012 | 10 | 50 | 10023 | | 55 | 10000 | 15 | 59 | 10003 | | 60 | 09990 | 1611 | 61 | 10000 | | 70 | 09977 | 20 | 68 | 09990 | | 80 | 09970 | 25 | 77 | 09981 | | 90 | 09967 | 30 | 86 | 09976 | | 100 | 09967 | 35 | 95 | 09974 | | 110 | 09970 | 40 | 104 | 09974 | | 120 | 09974 | 45 | 113 | 09976 | | 130 | 09979 | 50 | 122 | 09980 | | 140 | 09986 | 55 | 131 | 09985 | | 150 | 09994 | 60 | 140 | 09994 | | 160 | 10002 | 65 | 149 | 10004 | | 170 | 10010 | 70 | 158 | 10015 | | 180 | 10019 | 75 | 167 | 10028 | | 190 | 10029 | 80 | 176 | 10042 | | 200 | 10039 | 85 | 185 | 10056 | | 210 | 10052 | 90 | 194 | 10071 | | 220 | 1007 | 95 | 203 | 10086 | | 230 | 1009 | 100 | 212 | 10101 | +-----------+----------+----------+----------+----------+
In consequence of this variation in specific heat, the variation in the heat of the liquid of the water at different teives the heat of the liquid in a pound of water at terees Fahrenheit
The specific heat of ice at 32 degrees is 0463 The specific heat of saturated stea the other for that is difficult to define in any hich will not beWhen no liquid is present the specific heat of saturated steaative[14] The use of the value of the specific heat of steam is practically limited to instances where superheat is present, and the specific heat of superheated steam is covered later in the book
BOILER FEED WATER
All natural waters contain some impurities which, when introduced into a boiler, may appear as solids In view of the apparent present-day tendency toward large size boiler units and high overloads, the importance of the use of pure water for boiler feed purposes cannot be over-estimated
Ordinarily, ater of sufficient purity for such use is not at hand, the supply available ainst the cost of such treatment, there are many factors to be considered With water in which there is a marked tendency toward scale formation, the interest and depreciation on the added boiler units necessary to allow for the syste of certain units ain there is a considerable loss in taking boilers off for cleaning and replacing them on the line On the other hand, the decrease in capacity and efficiency acco an increased incrustation of boilers in use has been too generally discussed to need repetition here Many experiures reported as to this decrease, but in general, such figures apply only to the particular set of conditions found in the plant where the boiler in question was tested So many factors enter into the effect of scale on capacity and econoures on such decrease that will serve all cases, but that it is large has been thoroughly proven
While it is almost invariably true that practically any cost of treatment will pay a return on the investment of the apparatus, the fact must not be overlooked that there are certain waters which should never be used for boiler feed purposes and which no treatment can render suitable for such purpose In such cases, the only re of other feed supply or the e the feed water as in marine service
TABLE 14
APPROXIMATE CLassIFICATION OF IMPURITIES FOUND IN FEED WATERS THEIR EFFECT AND ORDINARY METHODS OF RELIEF
+-----------------------+--------------+-----------------------------+ | Difficulty Resulting | Nature of | Ordinary Method of | | fro | +-----------------------+--------------+-----------------------------+ | Sedi tanks, filtration, | | | | blowing down | | | | | | Readily Soluble Salts | Incrustation | Blowing down | | | | | | Bicarbonates of Linesia, etc | | addition of lime or of lime | | | | and soda Barium carbonate | | | | | | Sulphate of Lime | Incrustation | Treatment by addition of | | | | soda Barium carbonate | | | | | | Chloride and Sulphate | Corrosion | Treatnesium | | carbonate of soda | | | | | | Acid | Corrosion | Alkali | | | | | | Dissolved Carbonic | Corrosion | Heating feed Keeping air | | Acid and Oxygen | | from feed Addition of | | | | caustic soda or slacked | | | | lime | | | | | | Grease | Corrosion | Filter Iron aluulent Neutralization | | | | by carbonate of soda Use | | | | of best hydrocarbon oils | | | | | | Organic Matter | Corrosion | Filter Use of coagulent | | | | | | Organic Matter | Prie) | | connection with coagulent | | | | | | Carbonate of Soda in | Prie quantities | | supply If froe | +-----------------------+--------------+-----------------------------+
It is evident that the whole subject of boiler feed waters and their treatineer A brief outline of the difficulties that estion as to acertain of these difficulties is all that will be attempted here Such a brief outline of the subject, however, will indicate the necessity for a chemical analysis of any water before a treat the treatment in each case to the nature of the difficulties that ives a list of irouped according to their effect on boiler operation and giving the custo difficulty to which they lead
Scale--Scale is for of impurities in the feed water in the form of a more or less hard adherent crust Such deposits are due to the fact that water loses its soluble power at high teh, due to evaporation, that the impurities crystallize and adhere to the boiler surfaces The opportunity for formation of scale in a boiler will be apparent when it is realized that during a month's operation of a 100 horse-power boiler, 300 pounds of solid rains per gallon, while so and aters contain sufficient to cause a deposit of as high as 2000 pounds
The salts usually responsible for such incrustation are the carbonates and sulphates of lieneral deals with the getting rid of these salts more or less completely
TABLE 15
SOLUBILITY OF MINERAL SALTS IN WATER (SPARKS) IN GRAINS PER U S GALLON (58,381 GRAINS), EXCEPT AS NOTED
+------------------------------+------------+-------------+ |Terees | +------------------------------+------------+-------------+ |Calcium Carbonate | 25 | 15 | |Calciunesiunesium Sulphate | 30 pounds | 120 pounds | |Sodium Chloride | 35 pounds | 40 pounds | |Sodium Sulphate | 11 pounds | 50 pounds | +------------------------------+------------+-------------+
CALCIUM SULPHATE AT TEMPERATURE ABOVE 212 DEGREES (CHRISTIE)
+------------------------------+----+----+-------+----+---+ |Terees Fahrenheit|284 |329 |347-365| 464|482| |Corresponding gauge pressure | 38 | 87 |115-149| 469|561| |Grains per gallon |455|327| 157 |105|93| +------------------------------+----+----+-------+----+---+
Table 15 gives the solubility of these rains per U S gallon (58,381 grains) It will be seen fronesiurees, and calciurees becoreatly so as the temperature increases
Scale is also for of mud and sediment carried in suspension in water This may bake or be ceredients