EGGS IN COLD STORAGE. 57 



and if there is any air leakage, it will be outwardly 

 from the room exactly the way we want it to go. 

 Having- brought our subject to the point where it is 

 found that the best way to ventilate is by the use of 

 fans forcing- the air into the storag-e room, we will 

 determine what type of fan is best adapted to our 

 needs. What is said of fans for ventilation is equally 

 true if they are to be used for forced air circulation, 

 described under head of circulation. 



It is admitted by a majority of experts on air mov- 

 ing- machinery that the disk or propeller wheel ty pe type of fan - 

 of fan, throug-h which the air moves parallel to the 

 axis of fan, is not efficient or desirable for work where 

 the air has to travel throug-h a series of tortuous air 

 ducts, as in the forced air circulation system for cold 

 storag-e work, or for ventilation purposes where there 

 is some resistance. Where any resistance of import- 

 ance is encountered, the disk fanjnust be driven at a 

 hig-h rate of speed, and at an immense loss of power, to 

 compel it to deliver its full quota of air. Another dis- 

 advantage of the disk type is the difficulty of belting 

 to the shaft, or of g-etting- power to the fan in any 

 form, if it is inclosed entirely in an air duct. The disk 

 type will therefore be dismissed, and the well known 

 centrifug-al, or peripheral discharg-e fan taken up. 



This type of fan draws the air in at its center Advantages of 



J r the centrifugal 



parallel to the shaft, and delivers it at rig-ht ang-les 

 the shaft at the periphery or rim of the fan wheel, 

 the law g-overning- its action being- the well under- 

 stood centrifug-al force, which is commonly illustrated 

 when we see the mud fly from a bug-g-y wheel or the 

 water off a grindstone. The advantag-e of these fans 

 over the disk type is that the centrifugal action set 

 up by the rotary motion of the fan is utilized to give 

 velocity to the air in its passage over the fan blades. 

 In the selection of a fan for the purpose of forced cir- 

 culation in the storage room, or for forcing in fresh 

 air for ventilation, it should be noted that a large slow 



