In this paper

we have investigated the influences of heating surfaces

using copper

brass

stainless steel

nickel-plated

and chromium-plated heating suffaces. We found that

brass surface gave the highest a

while chromium-plated surface the lowest. This can be explained by the fact that the contact angle between liquids and metallic surfaces are different. The influences of heating surfaces are important only when the heat flow is comparatively low

such as q≤40000 kcal/m2.hr; while for higher heat flow

such as q≤1.5×105 kcal/m2.hr

the influences of heating .surfaces are not apparent. With heating surfaces of the same material

we found that aged surfaces gave lower ?than fresh surfaces

but the slopes of a - f(q) relationship are the same. For scaled surfaces

?is not only lower than both fresh and aged surfaces

the slope of a = f(q) is also flater; this is due to the heat resistence offered by the deposited scale. For heating surfaces of the same geometrical form

the dimension is not essential for ordinary cases

but for experimental apparatus of extremely small sizes

such as single heating wires of diameter less than 0.4 mm

or small circular plate of diameter less than 10 mm

the influences of dimension are not negligible. Finally

we have investigated the heat transfer coefficient of boiling solutions (5% - 20% NaCl solutions) The result is that for dilute solutions

the decreasing rate of a is rather high

while for concentrated solutions

the decreasing rate of ?is not so apparent. When correlated with dimensionless groups

we found that the equation suggested by P. H. KPY>KHJIHH may be used for calculations of salt solutions

but the following corrected form is found to be more satisfactory

with error not greater than±7%

The experiments were carried out with boiling liquids outside horizontal tubes (of diameters 25 - 60 mm) and above horizontal circular plates (of diameters 10 and 15 mm). The heat flow range of horizontal tubes is 1300-40000 kcal/m2. hr

while that of the horizontal plates is 20

000-900

000 kcal/ m2.hr.