1-s2.0-s0144860904000172-main

7/29/2019 1-s2.0-S0144860904000172-main

1/17

Aquacultural Engineering 31 (2004) 99115

Design of high efficiency surface aeratorsPart 2. Rating of surface aerator rotors

Beatriz Cancino

Department of Food Engineering, Universidad Catlica de Valparaso, Waddington 716, Valparaso, Chile

Received 1 April 2003; accepted 14 March 2004

Abstract

This paper is the second part of a three part work about surface aerator design for aquaculture. In this

work, the rotors for oxygen mass transfer developed in the first part were tested. Tests were conducted

on 23 different rotor configurations defined by the type of propeller, the inlet and exit angles of the

blades and the percentage of immersion. The Kinetic 3 propellerdesigned using the criteria of anaxial flow pump with a diameter of 94 mm, an inlet angle of 11 and an exit angle of 25yielded

the highest aeration efficiency at 10 C: 1.769 kg O2/kWh (SAE = 1.805kgO2/kWh). The Conrad

propellerdesigned using other criteriawith a diameter of 104 mm, an inlet angle of 25 and an

exit angle of 12, yielded the highest value for the global mass transfer coefficient at 10 C: 3.249 h1.

2004 Elsevier B.V. All rights reserved.

Keywords: Surface aerator design; Surface aerator efficiency

1. Introduction

Surface aerators are machines used to artificially increase the amount of oxygen available

in ponds or water tanks and are widely used for aquaculture. This work presents the second

part of a study about the aeration efficiency of centrifugal surface aerators. In the first part,

the main equations describing the transfer of oxygen to the water were shown as well as

the equations related to the design of the rotor. Finally, 10 different types of rotors were

presented in order to be tested in this second part.

The principal component of the centrifugal surface aerator is the rotor. This means that

the kinetics of the surface aerator can be defined when the following are identified: the type

Tel.: +56-32-274226; fax: +56-32-274205.

E-mail address: [email protected] (B. Cancino).

0144-8609/$ see front matter 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.aquaeng.2004.03.003

7/29/2019 1-s2.0-S0144860904000172-main

2/17

100 B. Cancino / Aquacultural Engineering 31 (2004) 99115

Table 1

Summary of aerator efficiency

Type of aerator Power (kW) SAE (kg O2/kWh) References

Paddle wheel 9.13.6 1.291.97 Busch et al. (1984)

Paddle wheel 0.96 2.96 Ahmad and Boyd (1988)

Paddle wheel 0.82 1.641 Rmmler (1992)

Paddle wheel 0.45 2.75 Boyd et al. (1988)

Venturi aerator N/A 1.22.4 Colt and Tchobanoglous (1981)

Difussed air systems: fine bubble N/A 1.22.0 Colt and Tchobanoglous (1981)

Surface aerator 30112 2.11.8 Stukenberg (1984)

Low speed surface aerator N/A 1.22.4 Colt and Tchobanoglous (1981)

High speed floating surface aerator N/A 1.22.4 Colt and Tchobanoglous (1981)

Centrifugal surface aerator 1.09 1.349 Rmmler (1992)

N/A: not available.

of propeller, the inlet and exit angles of the blades and the rotors immersion percentage.

Table 1 shows a summary of the values of AE for different aeration systems as given by

different authors.

The aim of this second part was to test the oxygen mass transfer of the rotors developed

in the first paper. The experimental tests were divided in two groups. The first experiments

were used to determine value of Q (water flow splashed by the aerator) and the second

group of experiments focused on the aeration.

2. Water flow test

The water flow tests were made for each rotor configuration as defined by the type of

propeller (or rotor), the inlet and exit angles of the blades and the percentage of immersion.

The percentage of immersion is the quotient between the immersion depth and the height

of the blade, multiplied by a hundred.

The types of the propellers used were presented in the first part of this work (Table 2).

The configuration for the water flow tests is shown in Fig. 1.

A 100 W dc motor with a nominal velocity of 1800 rpm was used in these tests. Thispower was approximately the upper limit used in the experiments. As was shown in the first

part of this work, all the parameters that defined the characteristics of the propellerssuch

as the inlet and exit angles of the blades and the percentage of immersionhave an influence

on the power used for aeration.

Considering the latter, before beginning the experiments we tested the range in which

each parameter could be varied to assure that the power rating of the motor would not be

exceeded.

The depth of the rotor inside the water or immersion depthwhich is defined by the

percentage of immersionwas tested. As the rotor was submerged the flow of splashed

water increased, but this required a greater amount of electrical power. The minimum depthis defined as having the propeller completely out of the water and a maximum depth consists

in the total immersion of the propeller so that it stirs the water without splashing.

7/29/2019 1-s2.0-S0144860904000172-main

3/17

B. Cancino / Aquacultural Engineering 31 (2004) 99115 101

Table 2

Results of the aeration efficiency tests at the test temperature

Kind of rotor Angle () % Immersion kLa (h1) Temperature

(C)

rpm Power (W) Q/P (m3/s W)

Flat 1 60 58 1.6299 17.4 930 108 12.925

Flat 1 45 62 2.1721 19.4 1670 109.8 17.9

Flat 2 45 164 2.7854 20.4 1110 79.04 20.769

Flat 3 45 124 1.9919 19.6 1900 51.03 21.037

Flat 3 45 152 2.6088 19.9 1880 58.56 23.604

Flat 3 60 140 2.4225 19.9 1850 65.34 20.439

Flat 3 70 109 2.445 19.6 1820 77.19 25.072

Flat 4 30 172 2.3019 18.6 1820 71.34 21.113

Flat 4 30 228 2.5989 18.6 1780 85.4 32.122

Flat 4 45 124 2.846 15.7 1760 87.12 21.067

Flat 4 45 152 3.3734 21.8 1630 109.35 25.950Flat 4 60 77 1.7375 16.2 1720 79.2 47.512

Flat 4 60 110 2.5032 21.7 1610 124.8 19.253

Kinetic 1 21, 35 69 1.3483 22.5 1910 53.24 22.204

Kinetic 1 21, 35 96 1.863 19.9 1870 68.32 31.572

Kinetic 1 21, 35 119 2.7513 19.8 1810 77.44 N/A

Kinetic 2 26, 42 68 1.8256 19.8 1860 70.47 17.491

Kinetic 2 26, 42 94 2.7291 19.7 1800 87.84 23.748

Kinetic 2 26, 42 233 2.6438 19.5 1750 104.06 40.121

Kinetic 3 11, 25 92 1.6721 22.5 2020 24.6 38.477

Conrad 25, 12 238 3.918 17.9 1720 93.6 75.61

German 1 21, 36 235 3.1472 17.9 1670 110.4 76.11

German 2 24, 74 174 3.5138 17.9 1680 88.8 79.70

N/A: not available. Experiments with a large amount of flow. Experiments chosen by chance.

Fig. 1. Diagram of the installation used for the water flow tests.

7/29/2019 1-s2.0-S0144860904000172-main

4/17


In previous experiments, a test tank was prepared with an auxiliary pond to provide

water using a centrifugal pump. A flow regulation valve and a rotameter were installed

at the output of the auxiliary pond in order to measure the flow that went to the test tank

which had the aerator. A valve was used to keep the water level constant in the test tank byeither opening or closing it. The aerator flow was measured indirectly by the rotameter at

the centrifugal pumps output. However, these first experiments could not be done for the

final tests presented in this work because the return pump was not large enough.

In these new experiments, the immersion depth was fixed, then the space between the

aerator and the tank was covered with a plastic sheet. Fig. 1 shows how the aerators

splashed water flow was measured. Once the motor was started, the time and water level

were measured. Meanwhile, the current and the voltage of the dc motor were recorded.

The motors speed was measured with a special electronic device built and designed for

these experiments. A special device was necessary because the space between the axis

and the bottom plastic cover of the motorsee Fig. 4 in Part 1was too small for the

available sensors. Once the waters height difference with respect to the initial conditions

was approximately 10 cm, the experiment concluded and the motor was turned off. This

experiment was repeated more than five times for each configuration. The results of these

experiments are shown in Table 1. In that table, there is only one case in which it was not

possible to measure the amount of water thrown due to the instability of the system. In the

aeration experiments, current, voltage and rpm were measured in order to control the water

flow thrown by the aerator. In general, no significant differences were found between the

results from these two kinds of experiments.

The relationship between the height and the diameter of the tank used for the water flowtest was 0.73:1.

The Q/P ratio was parameter chosen to compare, evaluate and select the best propellers.

Additionally, rotors able to throw large amounts of water were also chosen, as long as the

power consumption was below 100 W. This last consideration was made in order to allow

a possible error margin in which the maximum Q/P rate would not imply a maximum AE

value.

3. Method used for the aeration tests

The aeration tests were carried out using the sulfite method for surface aerators described

by Boyd (1986), Boyd and Watten (1989), Ppel (1984), Wagner (1997), ASCE Standard

(1992) and Stukenberg et al. (1977). The concentration of dissolved oxygen was measured

with two polarographic oxygen meter sensors. The sensors used in this work correspond

to two commercial sensors: a YSI sensor MEA model and a Edress+Hauser sensor. Both

sensors can be used with fluid velocity rates lower than 0.025 m/s. This characteristic is

very important for accurate measurements in the tanks.

The cobalt chloride catalyst was not used during these tests since it is considered haz-

ardous to human health (there are safety regulations applicable in Chile).

The dissolved oxygens saturation concentration (Cs) used for calculating the kLa wasestimated using the highest dissolved oxygen concentration for each test. In all the tests, this

value was higher than 90% of the theoretical saturation concentration of dissolved oxygen

7/29/2019 1-s2.0-S0144860904000172-main

5/17


Fig. 2. Picture of the installation used for the aeration efficiency tests.

expected by using Eq. (3) in Part 1. The values of C (dissolved oxygen concentration)measured during the experiments were graphed to help to find the value of Cs.

The testing pond had a volume of 4 m3, a rectangular shape, and a depth of 1 m. Drinking

water was used and the conductivity was kept under 1500S/cm. The motor used for

these experiments was the same 100 W dc motor used for the Q/P tests. The voltage and

current were measured for these experiments in order to guarantee that the same or very

similar amounts of power would be used as in the Q/P experiments. Fig. 2 shows the test

configuration. The measured power and volume from the aeration efficiency tests were used

for calculating the values of the AE.

To calculate the kLa coefficient (mass transfer coefficient) the semilogarithmic method

was used. This method consists in plotting the natural logarithm of the oxygen concentration

deficit against the time of aeration (see Eq. (1) in Part 1). The deficit was calculated from

the difference between the oxygen concentration (C) and the saturation concentration of

the dissolved oxygen (Cs). The time interval was 1 min. The number data points used

to calculate each kLa value with this method was between 40 and 70. The mass transfer

coefficient was determined by plotting this data against the time of aeration and calculating

the best coefficient of determination (r2) (Boyd, 1986).

4. Results and discussion

Table 2 shows the results of the tests used to determine the kLa coefficient (mass transfer

coefficient) of the rotors that showed the highest values of Q/P according to previous

7/29/2019 1-s2.0-S0144860904000172-main

6/17


experiments (Cancino, 2001). In all the experiments, the kLa coefficient was calculated

with a coefficient of determination of at least 0.99.

Other testswere also included: two experiments that give a large amount of flow (indicated

with in Tables 2 and 3), two experiments chosen by chance (indicated by in Tables 2and3) and all the Kinetic, German and Conrad rotors tested in the Q/P experiments (Cancino,

2001). Fig. 3 shows the jet of water thrown by the different rotors.

Table 3 shows the aeration efficiency corrected for 10 and 20 C for the same experi-

ments.

4.1. Discussion on mass transfer coefficient

The mass transfer coefficient calculated using this method may have errors according to

results from more specialized publications which present a better evaluation of this coef-

ficient using a non-linear approach (ASCE Standard, 1992; Wagner, 1997). Nevertheless,

the error should be constant in all the measurements. Because the method used requires a

straight line to fit the data, the error could be reduced if the linear regression coefficient

of the chosen line is high. In that case the slope of the line would accurately represent the

oxygen transferred to the water. In fact, this was the case in the tests, given that the linear

regression coefficient, r2, was greater or equal to 0.99.

If we suppose that an error does exist, the values of the mass transfer coefficients could

be used anyway because the intention here is to find relationships using equations and

establishing comparisons between them.

Table 2 shows the revolutions per minute (RPMs) of the different rotors which varyfrom 930 rpm for Flat 1 up to 2020 rpm for Kinetic 3. This variation is due to the

variation in the immersion depth and inlet angle of the different rotors. These variations in

the RPMs effect the variations in the amount of water thrown and the power consumed by

the aerator.

When the results are compared, for example the results for Flat 1, it can be observed

that for almost the same amount of power (108110 W) the RPMs can vary by as much as

factor of two. This behavior is produced because when the blades attack angle (inlet angle)

is softened, changing it from 60 to 45 the rotor may spin with more ease, reducing the

energy per unit time used by the aerator.

When the inlet angle is changed in this type of blade, the immersion depth changesimmediately even though no other adjustment is made to the aerator. This is caused because

the blade is turned from the vertical axis to the horizontal axis, increasing the horizontal

component and reducing the vertical. In this manner, the water thrown is increased due to

the fact that a greater amount of the blade is in contact with the water. Additionally, the

mass transfer coefficient also increases along with Q/P, in accordance with the hypothesis

that an increase in the flow rate implies an increase in kLa.

Nevertheless, this work does not pretend to undertake a separate analysis for each type

blade, instead the aim is to identify the components common to all the blades studied in

order to find the best or optimum configuration. The behavior of kLa10 as a function of

the immersion percentage, for all the blades, as can be seen in Fig. 4. In that figure itmay be noted that as the percentage of immersion grows, the value ofkLa10 also tends to

increase.

7/29/2019 1-s2.0-S0144860904000172-main

7/17

Table 3

Results of the aeration efficiency tests corrected at 10 and 20 C

Kind of rotor Angle (

) Immersion (%) kLa10 (h1

) OTR10 (g/m3

h) Q/P (m3

/s kW) AE1

Flat 1 60 58 1.268 15.440 0.012925 0.52

Flat 1 45 62 1.738 19.622 0.0179 0.67

Flat 2 45 164 2.177 24.573 0.020769 1.18

Flat 3 45 124 1.586 17.909 0.021037 1.29

Flat 3 45 152 2.063 23.29 0.023604 1.51

Flat 3 60 140 1.916 21.627 0.020439 1.32

Flat 3 70 109 1.947 21.983 0.025072 0.94

Flat 4 30 172 1.877 21.193 0.021113 1.12

Flat 4 30 228 2.119 23.928 0.032122 1.06

Flat 4 45 124 2.17 24.504 0.021067 1.04

Flat 4 45 152 2.55 28.789 0.025950 1.02Flat 4 60 77 1.5 16.934 0.047512 0.79

Flat 4 60 110 1.897 21.413 0.019253 0.66

Kinetic 1 21, 35 69 1.002 11.317 0.022204 0.84

Kinetic 1 21, 35 96 1.473 16.632 0.031572 0.97

Kinetic 1 21, 35 119 2.181 24.62 N/A 1.20

Kinetic 2 26, 42 68 1.447 16.337 0.017491 0.88

Kinetic 2 26, 42 94 2.168 24.48 0.023748 1.05

Kinetic 2 26, 42 233 2.11 23.827 0.040121 0.87

Kinetic 3 11, 25 92 1.24 14.035 0.038477 1.76

Conrad 25, 12 238 3.249 36.677 0.07561 1.45

German 1 21, 36 235 2.609 29.461 0.07611 0.98

German 2 24, 74 174 2.913 32.893 0.07970 1.37

N/A: not available. Experiments with a large amount of flow. Experiments chosen by chance.

7/29/2019 1-s2.0-S0144860904000172-main

8/17


From the analysis made in Part 1, it was shown that kLa could be increased chang-

ing the setup of the equipment, resulting in an increase of the amount of water splashed

(Q). Fig. 5 shows the results of these experiments. It can be seen that the previous af-

firmation is observed experimentally, with a correlation of r2 = 0 indicatingthat when the flow is increased, the global mass transfer coefficient also tends to

increase.

Fig. 6 shows the behavior of the kLa10 with respect to the Q/P rate. The behavior is similar

to the one seen in Fig. 5, in other words kLa10 increases along with the Q/P rate.

Fig. 3. Jet water thrown by different rotors. The immersion percentage is the quotient between the immersion

depth and the height of the blade multiplied by 100.

7/29/2019 1-s2.0-S0144860904000172-main

9/17


Fig. 3. (Continued).

4.2. Discussion on aeration efficiency

Fig. 7 shows a summary of AE in function ofQ/P ratios for all the types of rotors. Figs. 8

and 9 show AE in function of flow (Q) and the kLa, respectively.

7/29/2019 1-s2.0-S0144860904000172-main

10/17


Fig. 3. (Continued).

There is no linear relationship between AE and Q/P or Q (Figs. 7 and 8). In Fig. 7, for

example, in spite of the fact that in the value of AE generally increased with the Q/P ratio,

there are values ofQ/P that give higher aeration efficiencies that the highest values of Q/P.

In other words, there are rotor configurations where the systems behavior gives maximum

aeration efficiency.

In the previous section, we observed that when the flow is increased the global mass

transfer coefficient increases. Nevertheless, if we observe the behavior of AE in relation to

the amount of flow (see Fig. 8), this increment cannot be clearly appreciated. This is due tothe effect of the power on the aeration efficiency (shown in Eq. (5) of the first part). On the

other hand, observing the influence ofQ/P over kLa10, shown in Fig. 6, a tendency towards

an increase of the latter with an increase of the first is observed.

Fig. 4. Variation ofkLa10 as a function of immersion percentage.

7/29/2019 1-s2.0-S0144860904000172-main

11/17


Fig. 5. Variation ofkLa10 as a function of flow (Q).

The behavior of the AE for as a function of the percentage of immersion for all the

propellers is shown in Fig. 9. Fig. 9 shows that as the percentage of immersion grows,

AE increases evenly until the immersion percentage is over 200%, point in which where

there is a fall in the value of AE. Additionally, there is another point that lies on the

graph that is greater that the rest of the values. These two points correspond to the max-imum values of efficiency of the rotor systems that were analyzed. The highest value

of AE (1.8 approximately) corresponds to the Kinetic 3 rotor. This propeller was de-

signed using the similitude to an axial flow pump criterion. Fig. 10 shows the same

behavior of AE and percentage of immersion but without the value for Kinetic 3 ro-

tor. The polynomial correlation to this data is shown in the figure and the value of r2 is

0.5396.

Analyzing the behavior of the proposed propellers with respect to AE, it would be ap-

propriate to design the propellers taking advantage of their similitude to an axial flow

pump. Since the Kinetic 3 propeller is the one with the highest AE, it follows that the val-

ues recommended by that method be used in order to have a large flow at a low height. Thecalculated Q/P ratio (0.031) is similar to one obtained experimentally (0.038). However,

the power and the resulting flow are well below the design specifications.

7/29/2019 1-s2.0-S0144860904000172-main

12/17


Fig. 6. Variation ofkLa10 with respect to Q/P ratio.

Fig. 11 shows the AE variation with respect to kLa10. The behavior of the AE according

to the increase of kLa10 is not completely a straight line. In Fig. 11, a maximum value ofAE can be found which corresponds to Kinetic 3 propeller.

If we compare the values of kLa10 for the different propellers, we find that highest

values correspond to the German and Conrad propellers, being this last one the one that

Fig. 7. Variation of aeration efficiency as a function of Q/P.

7/29/2019 1-s2.0-S0144860904000172-main

13/17


Fig. 8. Variation of aeration efficiency as a function of Flow (Q).

presents the highest kLa10 (3.249 h1). The Conrad propeller design was based on a ships

propeller (not by the authors). Probably this criterion would be more suitable for future

designs of the propellers of surface aerators since its aeration efficiency is the third best one

(1.45 kg O2/kWh).

Fig. 9. Variation of AE for all rotors as a function of immersion percentage.

7/29/2019 1-s2.0-S0144860904000172-main

14/17


Fig. 10. Variation of AE for all the rotors excepted the Kinetic 3 rotor, as a function of immersion percentage.

The propeller configurations (defined by type of propeller, inlet and exit angles and

immersion percentage) that yield the best AE (over 1.2 kg O2/kWh) can be seen in Table 4

where they are shown ranked according to AE, from the greatest to the least. Table 5 shows

the propeller configurations that yield the best values of kLa10.

Fig. 11. Variation of aeration efficiency as a function of kLa10.

7/29/2019 1-s2.0-S0144860904000172-main

15/17


Table 4

Propeller configurations that yield values of aeration efficiency greater than 1.2 kg O2/kWh

Propeller AE (kg O2/kWh)

Kinetic 3 (11, 25) 1.769

Flat 3 (45, 152%) 1.511

Conrad (12, 238%) 1.450

German 2 (74, 174%) 1.371

Flat 3 (60, 140%) 1.324

Flat 3 (45, 124%) 1.299

Kinetic 1 (35, 119%) 1.208

A significant difference could be noticed between the types of water jets produced by

the propellers under study (see Fig. 3). The type of jet is related to the aeration efficiencyas shown in Table 4, where it can be seen that a jet with a large water mass behaves well.

The exception to this general behavior is the Kinetic 3, which has the highest value of

AE. In this rotor the aeration is produced by droplets and not with a solid jet of water. This

behavior is due to the relatively low expenditure of energy used to throw the jet, which is

responsible for the high AE values.

The jet created by the German 2 propeller (see Fig. 12) is a large mass of thrown water.

If a relationship is established according to the value of kLa10, then when using the

propellers in Table 4 the jet with the best oxygen transfer values is the one with the lowest

dispersionthat is, the one with the largest masses of water as opposed to droplets.

When considering which is the best propeller for a gyroscopic surface aerator, not onlyshould the aeration efficiency (AE) be considered, but also the oxygen mass transfer veloc-

ity. This parameter is defined through kLa. The reason for this is that the aerator should be

capable of delivering at least a minimum amount of oxygen to the fish. If the aerator cannot

deliver that amount, its use would be meaningless. This is why the minimum amount of

oxygen to be delivered by the aerator should be defined when designing the equipment.

Another interesting parameter to be compared between designs is the global mass transfer

coefficient as a function of the power consumption for the different propellers, the values

of kLa10, starting with the highest, are shown in Table 5. According to this, the best pro-

peller, given a minimum value of kLa10 equal to 1.2, is the Conrad with 3.249 h1. The

classification of the propellers, ordered from best to worst, is shown in Table 5.

When comparing the results obtained for the AE with those ofTable 1, it may be seen

that these results are with the ranges of the experiments of Busch et al. (1984), Rmmler

Table 5

Propeller configurations that yield values of mass transfer coefficient greater than 2.2 h1

Rotors kLa10 (h1) Power (W)

Conrad (12, 238%) 3.249 93.6

German 2 (74, 174%) 2.913 88.8

German 1 (21, 36) 2.609 110.4Flat 4 (45, 152%) 2.550 109.35

Flat 4 (70, 100%) 2.315 116.16

7/29/2019 1-s2.0-S0144860904000172-main

16/17


Fig. 12. A picture of the water jet created by the gyroscopic aerator using the German 2 type propeller, seen in

full scale.

(1992) and Colt and Tchobanoglous (1981) but are less than the values obtained by Ahmad

and Boyd (1988) and by Boyd et al. (1988). Nevertheless, all these studies were realized

with aeration systems other than centrifugal surface aerators. On the contrary, the last three

types of aerators shown in Table 1 do indeed correspond to centrifugal surface aerators as

described in this work. The values of AE (see Table 4) are found in the ranges given by

those last three authors.

Wagner (1997) gives a correlation of AE with respect to the power density of the centrifu-

gal surface aerator. He defines the power density as the power required to aerate each unit

of volume of water (W/m3). Therefore, it is necessary to identify the value of this parameter

in order to obtain the value of AE.

The volume of the testing pond in this work was of 4 m3 and the power was approximately

100 W. Therefore, the power density for the experiments was of 100/4 = 25 W/m3.

According to Wagner (1997) with 25 W/m3, for a well mixed water tank, the AE10 is

between 1.3 and 1.4 kg O2/kWh. Finally, the experimental value obtained for the Kinetic

3 rotor is of 1.769 kg O2/kWh which is better than that reported by Wagner for an aeratorof the same type.

5. Conclusions

From the results, it can be concluded that a propeller configuration (defined by the kind

of propeller, the inlet and exit angles and the immersion percentage) that throws masses of

water instead of droplets should be preferred for use in centrifugal surface aerators.

The Kinetic 3 propellerdesigned under the criteria of an axial flow pump with a

diameter of 94 mm, an inlet angle of 11 and an exit angle of 25yielded the highest aer-ation efficiency at 10 C (5243) 1.769 kg O2/kWh (SAE = 1.805kgO2/kWh). The Conrad

propellerdesigned using other criteriawith a diameter of 104 mm, an inlet angle of 25

7/29/2019 1-s2.0-S0144860904000172-main

17/17


and an exit angle of 12, yielded the highest value for the global mass transfer coefficient

at 10 C: 3.249 h1.

References

Ahmad, T., Boyd, C.E., 1988. Design and performance of paddle wheel aerators. Aquacult. Eng. 7, 3962.

ASCE Standard, 1992. Measurement of Oxygen Transfer in Clean Water, second ed., The American Society of

Civil Engineers.

Boyd, C., 1986. A method for testing aerators for fish tanks. Prog. Fish Cult. 48, 6870.

Boyd, C., Ahmad, T., La-fa, Z., 1988. Evaluation of plastic pipe, paddle wheel aerators. Aquacult. Eng. 7, 6372.

Boyd, C., Watten, B., 1989. Aeration Systems in Aquaculture. CRC Press. CRC Crit. Rev. Aquat. Sci. 1 (3)

425472.

Busch, R.L., Tucker, C.S., Steeby, J.A., Reames, J.E., 1984. An evaluation of three paddlewheel aerators used for

emergency aeration of channel catfish ponds. Aquacult. Eng. 3, 5969.

Cancino, B., 2001. Optimizacin y estudio de un aerador superficial para pozas de cultivo de peces con suministro

de energa por paneles fotovoltaicos. Doctoral Thesis, Universidad Tecnica Federico Santa Mar a, Valparaiso,

Chile.

Colt, J., Tchobanoglous, G., 1981. Design of aeration system for aquaculture. In: Allen, L.J., Kinneys, E.C. (Eds.),

Proceedings of the Bio-engineering Symposium for Fish Culture. American Fisheries Society, Bethesda, MD,

pp. 138148.

Ppel, H.J., 1984. Entwicklungs Tendenzen der Belftung beim Belebung verfahren. Wasser und Boden, vol. 5.

Darmstadt, pp. 206213.

Rmmler, F., 1992. Beurteilung des Sauerstoffeintrags von Beluftern, vol. 2. Fischer and Teichwirt, pp. 5354.

Stukenberg, J., 1984. Physical aspects of surface aeration design. J. WPCF 56 (9), 10141021.

Stukenberg, J.R., Wahbeh, V.N., McKinney, R.E., 1977. Experiences in evaluating and specifying aerationequipment. J. WPCF (January), 6682.

Wagner, M., 1997. Sauerstoffeintrag und Sauerstoffertrag von Belftungssystemen und deren Bestimmung mit

Modernen Messmethoden. Institut WAR: Wasserversorgung Abwassertechnik-Abfalltechnik. Umwelt-und

Raumplanung der TU Darmstadt. No. 100.

1-s2.0-s0144860904000172-main

Documents