This work was planned to study the effects of gas and liquid rates on the true gas-film coefficients of heat and mass transfer between gas and liquid in packed columns. Adiabatic humidification tests were made in a column, 254mm in i.d., dumped-packed with 15, 25 and 35mm porcelain Raschig rings to a height of 320mm. The air, supplied by a blower, passed through an orifice, and then through a preheater to the column. Water was recirculated through the system by means of a pump, and was at the wet-bulb temperature after steady-state conditions had been attained. To minimize the end effects due to spray below and above the packed section, specially designed column as shown in Fig. 1 was employed. Humidities of the incoming and outgoing air were determined by means of wet and drybulb, thermometers; the dry-bulb temperature of air just above the packings was calculated from the humidity and the wet-bulb temperature.
Data and calculated results are shown in Tables 1, 2 and 3. Superficial mass velocity of air G ranged from 700 to 2800 kg/m²·hr; superficial water velocity L ranged from 800 to 20000kg/m²·hr.The gas-film coefficient of heat transfer hGa[kcal/m³·hr·°C]for 25mm Raschig rings, for several water rates, were plotted against G in Fig. 2. Data were fitted by parallel straight lines having slopes of approximately 1.0. The effect of water rate was made clearer by Fig. 3 and Fig. 4, which also included the data for 15 and 35mm rings. It is evident that the increase of hGa with water rate is comparatively large at low water rate, and becomes very small at high water rate. The correlation was represented by
or by
Eq. (7) is sufficient for engineering purposes, for L of 1000 to 20000 kg/m²·hr, and Eq. (8) is considered suitable for extrapolation outside this range of L. Fig. 5 and Fig. 6 show the validity of these equations for the three kinds of Raschig rings.
The effects of G and L on the gas-film coefficient of water vapor transfer k'Ga [kg/m³·hr·ΔH] were quite similar to the effects on hGa. Fig. 7 shows the plot of k'Ga for 25mm Raschig rings against G at several water rates. The data for the three kinds of Raschig rings were plotted in Fig. 8 and Fig. 9, being correlated by
or by
The latter equation may be suitable for extrapolation outside the experimental range of L.
The ratio hGa/k'Ga calculated from Eqs. (7) and (9) or from Eqs. (8) and (10) was 0.26, the "Lewis relation" being nearly satisfied.
(H.T.U.)G for 25mm Raschig rings, for several water rates, was plotted against G in Fig. 10. As evident from Eqs. (6), (9) and (10), (H.T.U.)G is independent of G, at a given value of L.

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Water-cooling, tests were made using a column, 254mm i.d. and packed with 25-mm ceramic Raschig rings to a depth of 320mm. The results showed that the water-film offerred considerable resistance to enthalpy transfer between water and air. The water-film coefficient hLa [kcal/m3·hr·°C] was computed With the use of the empirical equation (5) for the gasfilm coefficient k'_Ga [Kcal/m³·hr·Δi] obtained by the authors from the data on the adiabatic humidification runs in the same apparatus. The correlations were
in which G and L were the mass velocities of gas and water respectively in kg per hour per square meter of gross cross section of the column.
The over-all coefficient K'Ga and (H.T.U.)OG Were also computed. The value of K'Ga ranged from 40 to 70% of that of k'Ga. It is to be noted that (H.T.U.)OG was far smaller than those For conventional grid towers.
Methods of seperating the over-all coefficient or (H.T.U.) into individual ones were suggested.

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空氣の減濕並びに冷水操作に於ける空氣の状態變化を知ることは,その機構を理解する上に於ても,またこれらの裝置の設計々算或いはその操作條件の選定を誤りなく行うためにも甚だ重要である。減濕操作に於ける空氣の状態變化については,既にKeevil及びLewisによつて研究されているが,しかし彼等の得た結果も僅かにその定性的傾向を與えているにすぎない。筆者はこの場合の空氣の状態變化を濕度圖表上に求める方法として,同一圖表上に施されたエンタルピ目盛を仲介とする近似的圖解方法を提案し,且つ同樣の方法により冷水操作に於ける空氣の状態變化を求めて,冷水塔に於ける空氣の温度變化に關する考察の一端を述べ,併せてこれらの場合に於ける温度差,濕度差並びにエンタルピに基く移動單位數の計算法を示した。

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