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Research Article
 

Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines



M. Mosa, Zhu Yuqun and A. Yattara
 
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ABSTRACT

In this paper an attempt has been made to develop an absorber for small-size absorption systems. A mathematical model and a computer code for evaluating the theoretical performance of such absorber were developed. This model and code take into account the essential parameters such as solution inlet and outlet conditions, cooling water inlet conditions and absorber geometry. Variation of solution temperature and concentration, cooling water temperature, absorption rate and heat duty across the absorber were presented graphically. Compared to the conventional absorber design, this absorber is expected to attain higher heat and mass transfer coefficients and wetting area and hence a better performance and a reduction in absorber size.

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  How to cite this article:

M. Mosa, Zhu Yuqun and A. Yattara , 2003. Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines. Journal of Applied Sciences, 3: 305-316.

DOI: 10.3923/jas.2003.305.316

URL: https://scialert.net/abstract/?doi=jas.2003.305.316

Introduction

Absorption machines have gained increased interest in the recent years. One of the disadvantages of such machine is its large size components especially the absorber which is the most critical component, and its characteristics have significant effect on overall system efficiency. Reduction of the absorber size needs a well investigation of the absorption process inside the absorber. In this aspect, many research have been theoretically conducted (Andberg and Vliet (1987), Jeong and Garimella (2002)) and many experiments has been carried out (Cosenza and Vliet (1990), Hoffmann (1996), Deng and Ma (1999)). Even though an improvement of absorber efficiency, by the development of tubes having higher efficiency and supply of surfactants, was reported (Yoon and Kim (2002), Beutler et al. (1996)), but this machines still facing difficulties to be adopted as a viable residential absorption system. Recently, Garimella (2000) presented and analyzed a miniaturization technology for absorption heat and mass transfer component. He preliminary modeled it for NH3-H2O system and concluded that such concept holds to the potential for the development of extremely small absorption system components. In this paper, the same concept was considered for LiBr-H2O absorbers with different modeling approach, design and simulation.

A full detailed description of the concept can be found in Garimella (2000) and briefly as follows: Short lengths of small diameter tubes are placed in square array to form one row, Figure (1.a). The second row is placed above the first row in a transverse orientation perpendicular to the tubes in the first row, Figure (1.b). A complete absorber then can be built in the same manner, Figure (1.c). Cooling water flows from bottom to the top through all the rows in series form or parallel through the rows of one pass and then in series through all passes. Strong solution enters from the top while the vapor enters, countercurrent to the solution, from the bottom.

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 1: Schematic of the concept: (a) one row (b) two rows and (c) complete absorber

Modeling and simulation
A mathematical model and computer code were developed to develop and simulate such absorber or simulate an already existing absorber. In this model, the solution film flow along one half of the tube is modeled as that along a vertical cooled wall with a length of half tube circumference, which is a model suggested by Wassenaar (1995). A schematic representation of the model is shown in Figure (2). Equations of momentum, energy and diffusion of mass and their specific boundary conditions for this situation are represented in four dimensionless combined ordinary differential equations as follows:

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(1)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(2)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(3)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(4)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 2: Schematic of the model

These equations describe the average mass fraction of water in the solution Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, the average solution temperature Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines the heat transferred to the cooling medium across the plate wall per unit width Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machinesand the mass transfer of the water vapor to the film per unit width Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines in one infinitesimal part of the film with length Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines as shown in Figure (2). A good estimate for the transfer numbers defined in Equations (1-4) are, Wassenaar (1995):

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(5a)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(5b)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(5c)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(5d)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(5e)

Then, these equations are solved numerically for a unit width of the plate, Khalid and Ali (2001), to give the final form as follows:

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(6)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(7)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(8)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(9)

where

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(10a)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines

(10b)


Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(10c)

Absorber design and simulation
The mathematical model developed in the preceding section can be adopted to design an absorber and simulate an already existing one. In this section absorber design and simulation are presented, respectively. Utilization of the developed mathematical model to design an absorber of such type for specific evaporator cooling capacity, the following design conditions should be given:

Evaporator load QE
System pressure P
Solution inlet concentration ξs,i
Solution inlet temperature Ts,i
Solution outlet concentration ξs,o
Solution outlet temperature Ts,o
Cooling water inlet temperature Tc,i

From the evaporator load and system pressure and using steam tables, vapor flow rate can be calculated. Then, equating this amount of vapor to the vapor to be absorbed inside the absorber Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, the solution flow rate inlet to the absorber Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines and solution outlet flow rate can be calculated as follows:

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(11)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(12)

Substituting Equation (11) into Equation (12) yields:

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(13)

As first step, general absorber geometry to meat the evaporator load is to be selected:

Tube outside diameter (do).
Tube inside diameter (di).
Tube length (L).
Number of tubes per row (NT/R).
Number of rows per pass (NR/P).
Number of passes (NP).

The algorithm for the solution of equations has constructed in C-Language. The flow diagram shown in Figure (3) describes the sequence of various operations. To avoid confusion, the following abbreviations were used for cooling water routine through rows, passes, and the whole absorber as shown in Figure (4).

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 3: Cooling water routine through (a) row, (b) pass and (c) absorber.

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 4: Schematic of one horizontal tube

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Row inlet cooling water temperature,
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Row outlet cooling water temperature,
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Pass inlet cooling water temperature,
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Pass outlet cooling water temperature,
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Absorber inlet water temperature,
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines : Absorber outlet water temperature.

From the above abbreviations it can be seen that

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(14)

1. First of all, the necessary parameters and fluid properties are set.
2. As simulation of one tube represents all the tubes in the same row, one tube is divided along the length into m sections (starting from the inlet) each of length (dL = L/m). Half circumference of the tube is divided into n equal parts as shown in Figure (4).
3. Starting from the most upper row of the most upper pass and at a particular section, the inlet conditions are established on the basis of input parameters such as mass flow rate per unit length per one side of the tube,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, inlet temperature,Τs,i, and concentration,ξs,i, of the solution.
4. The absorber cooling water outlet temperature,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, (which is also the outlet temperature of the most upper pass Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines) and the pass inlet temperature,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, (very close to the outlet temperature,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines) are assumed.
5. Under the input conditions to the tube, Equations (6-9) can be applied to the first part (i = 1) of the first section (j = 1). The inputs start with
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
then the outputs are used as inputs to (i = 2) at the same section (j =1) and so on to the last part (i = n) where the outputs are
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
All these processes are taking place at constant cooling water temperature Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines.
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(15)
6. Solution outlet temperature and concentration for each section is calculated as follows:
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(16)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(17)
And solution outlet flow rate
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(18)
7. Steps (5) and (6) are repeated for (j = 2, 3,…, m) with a new cooling water temperature, Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, at each section. This temperature can be obtained from the heat balance around the cooling water circuit as follows:
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(19)
8. Heat transfer to the cooling water from the row, Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, and the total mass flow rate of solution leaving the row, Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, are computed by:
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(20)

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
(21)
9. Solution temperature and concentration leaving the tube (the row) are computed by taking the average temperature and concentration over all sections (j=1,2,…m).
10. Steps (5-9) are repeated for the next rows (Ro = 2, 3,… NR/P) with the above row outlet conditions are used as inputs to the next row until the last row in the pass is reached.
11. Pass cooling water outlet temperature is computed by taking the average cooling water outlet temperature over all the rows of the pass. At this stage, if the difference between pass average outlet temperature and the assumed one is greater than a predetermined value,ξ1, the cycle is repeated with reducing the previously assumed Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines.
12. When the convergence for the upper pass is reached, the whole sequence of operation proceeds to the next pass with pass cooling water outlet temperature is set equal to the upper pass inlet temperature.
13. Steps (5-12) are repeated until the last pass is reached. At this stage, absorber cooling water inlet temperature,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, is compared with a specified value, (32°C). If the difference is greater than a predetermined value,ξ2, the cycle is repeated with reducing the previously assumed absorber cooling water outlet temperature,Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines.
14. Finally, conditions of the solution leaving the absorber (leaving the last row), Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, and Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machinesare compared with the required design ones. If these conditions are different from the design ones, absorber configuration, (tubes size, tube per unit row…etc), are changed and the whole sequence is repeated.
15. When the resulted outlet conditions are the same as the design ones the whole results are given and the program terminated.

This model and computer code was used to develop and simulate an absorber with the design conditions shown in Table (1.a). The absorber geometry selected by the code was shown in Table (1.b) whereas the absorber simulated performance is presented graphically in Figure (5-8).

Table 1: (a) design conditions and (b) selected absorber geometry
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines

Results and discussion:

Figure (5) shows the variation of solution and cooling water temperatures across the absorber and the corresponding solution concentration is shown in Figure (6).

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 5: Variation of solution and cooling water temperature across absorber rows

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 6: Variation of solution concentration across absorber rows

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 7: Variation of absorption rate and across absorber rows

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Fig. 8: Variation of heat duty across absorber rows

It can be seen that the solution temperature at the top of the absorber drops significantly as the solution is closed to saturation state, therefore absorption is very small and the cooling water duty is the sensible heat of solution. After this, absorption increases and solution temperature changes tend to stabilize. The cooling water temperature increases from bottom to top and jump periodically every 6 rows due to the change to the next pass. The solution concentration progressively decreases from top to bottom as vapor is absorbed into it.

Variation of vapor absorption rate across the absorber is shown in Figure (7). At the absorber inlet absorption rate is very small as mentioned before and then increases as the solution temperature drops and finally decreases uniformly as the difference between the solution and cooling water temperatures decreases. Figure (8) shows the variation of heat duty across the absorber. At the inlet heat duty is high even though absorption rate is small because of sensible cooling of the solution and then drops toward the bottom with periodic jump every new pass.

CONCLUSION

A mathematical model and a computer Code for development and simulation of a small-size absorption refrigeration machines using LiBr-H2O as working fluid were developed in this study. Operating conditions were selected as input to this model and code and the corresponding absorber geometry to meet these conditions were given as output. The resulted absorber performance was then simulated and presented graphically.

Nomenclature

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
= constants Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Biot number Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = specific heat capacity at constant pressure (kJ/kg °C)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = diameter (m) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = mass diffusivity of solution (m2/s)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Graetz number Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = specific enthalpy (kJ/kg)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = heat of absorption (kJ/kg) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = thermal conductivity (kW/m2 °C)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = length (m) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Lewis number
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = mass flow rate (kg/s) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = number
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = number of tubes Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Nusselt numberImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = pressure (kPa) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Prandtl numberImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = heat flow per unit length (kW/m) Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Renolds numberImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = Sherwood number Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = temperature (°C)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = mass fraction of water in solution (kg/kg)      
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = average mass fraction Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = coordinate along wall plate (m)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = coordinate perpendicular to the wall plate (m)      

Greek

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
= dimensionless mass fractionImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = average dimensionless mass fraction
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = solution film thickness Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = dimensionless temperatureImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = average dimensionless temperature
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = dimensionless heat of absorption
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = lithium bromide concentration (kg/kg)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = dynamic viscosity (kg/m.s)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = density (kg/m3)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = derivative of Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machineswith respect toImage for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines at constant Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines, ∂h/∂w (kJ/kg)
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = thermal diffusivity (m2/s)

Subscripts

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = sequence number      
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = absorbed Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = absorber
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = average Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = cooling water
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = equilibrium Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = interface or inside
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = sequence index Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = number
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = entrance or outside Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = refrigerant
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = solution Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = vapor
Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = wall      

Superscripts

Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = absorber Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = pass Image for - Development and Simulation of an Absorber for Small-size Libr-H2O Absorption Refrigeration Machines = row
REFERENCES
1:  Andberg, J.W. and G.C. Vliet, 1987. A simplified model for absorption of vapors into liquid films flowing over cooled horizontal tubes. ASHRAE Trans., 93: 2454-2466.
Direct Link  |  

2:  Beutler, A., I. Greiter, A. Wagner, L. Hoffmann, S. Schreier and G. Alefeld, 1996. Surfactants and fluid properties. Int. J. Refrigeration, 19: 342-346.
Direct Link  |  

3:  Cosenza, F. and G.C. Vliet, 1990. Absorption in falling water/LiBr films on horizontal tubes. ASHRAE Trans., 96: 693-701.

4:  Deng, S.M. and W.B. Ma, 1999. Experimental studies on the characteristics of an absorber using LiBr/H2O solution as working fluid. Int. J. Refrigeration, 22: 293-301.

5:  Garimella, S., 2000. Microchannel components for absorption space-conditioning systems. ASHRAE Trans., 106: 453-464.
Direct Link  |  

6:  Hoffmann, L., 1996. Experimental investigations of heat transfer in a horizontal tube falling film absorber with aqueous solutions of LiBr with and without surfactants. Int. J. Refrigeration, 19: 331-341.
Direct Link  |  

7:  Jeong, S. and S. Garimella, 2002. Falling-film and droplet mode heat and mass transfer in a horizontal tube LiBr/water absorber. Int. J. Heat Mass Transfer, 45: 1445-1458.
CrossRef  |  Direct Link  |  

8:  Khalid, A.J. and H.A. Lafta, 2001. Simulation of a simple absorption refrigeration system. Energy Convers. Manage., 42: 1575-1605.
CrossRef  |  Direct Link  |  

9:  Wassenaar, R.H., 1995. Falling film absorption: A discussion on three types of model and on the data reduction of absorption measurements. Proceedings of the 19th International Congress of Refrigeration, (ICR`95), Melbourne, pp: 34-38.

10:  Yoon, J.I. and E. Kim, 2002. Heat transfer enhancement with a surfactant on horizontal bundle tubes of an absorber. Int. J. Heat Mass Transfer, 45: 735-741.
CrossRef  |  Direct Link  |  

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