1. Republic of Iraq
Ministry of Higher Education
& Scientific Research
University of Kufa
By M.Sc. Hyder Mohammed Abdul Hussein
ABSTRACT
A theoretical study includes details flow turbulence in air-conditioned spaces with the determination of the
boundary conditions depending on the Iraqi Code of cooling is done in this research. Two kinds of two-
dimensional and three-dimensional ventilation problems have been considered:
(a) isothermal ventilation in simple rooms.
(b) non-isothermal ventilation with coupled heat or mass transfer.
The investigation has studied the flow and thermal conditions for four different diffusers (displacement, grille,
slot, and square diffusers). The dimensions of the of the physical model are (5.16×3.65 m) with (2.43 m high). The
supply condition for four diffusers are (displacement (0.0768 kg/s), grille (0.0768 kg/s), slot (0.1410 kg/s), square
(0.750 kg/s)) and temperature at supply for all types is (15.0o
C), the return considered as the type of diffusers has
been imposed zero flow pressure and temperature at (24.0o
C).
A modified version of a three-dimensional computer program (fluent 6.3.26) by using finite-volume method was
used to simulate the complex flow with buoyant inside the model room. They have been investigated numerically
by using several turbulence models and the method solution by using k-ε and k-ω models.
A THEORETICAL STUDY OF A COLD AIR DISTRIBTION
SYSTEM WITH DIFFERENT SUPPLY PATTERNS

2. The Iraqi Code of Cooling limited the outdoor for Baghdad and indoor conditions are
listed in Table (1) and Table (2), respectively.
Table (1) Outdoor data for Iraq
Region
DBT in summer
(ºC)
RH %
in summer
The daily
(ºC)
Altitude
(m)
Latitude
N
Longitude
E
Baghdad 47 16 18.7 34.1 33.32 44.33
Table (2) Indoor conditions
DBT in summer
(ºC)
RH %
in summer
Air velocity
(m/s)
Human comfort 19 - 24 40 - 60 1.8 – 2
Recommended conditions
inside the office
23 - 26 40 - 50 0.13 – 0.23
Four types of diffusers are set in three orientations all south-facing and all cases
running as constant wall temperature, but not that all walls of office are exposed to
outside. For each type of diffuser three cases are chosen, the first case just eastern and
southern walls, the second case is only the southern wall and the third case is the
southern and western wall, and the ceiling wall in all cases is included.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

3. Displacement Diffuser
The inlet diffuser is located near the west wall, and the exhaust opening is at the center
of the ceiling
the objects (human, computers, tables, lamps and cabinets) are simulated.
Boundary conditions:
Supply diffuser: mass flow rate of 0.0768 kg/s , turbulence intensity of 4% .
Return: The outlet is specified as pressure outlet.
Thermal conditions:
• Computer 1: 171.43 W/m2
• Computer 2: 274.6 W/m2
• Human simulators: 41.9 W/m2
• Lamps: 37.78 W/m2
Turbulence modeling: Applying that the Realizable k-ε and the SST k-ω models.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

4. Computation meshes: (1,480,232) cells.
Numerical schemes: discretized using the second-order upwind scheme. For the
discretization of pressure, the PRESTO! (PREssure STaggering Option) scheme is used. The
SIMPLEC scheme is used for the pressure-velocity coupling.
Summary of boundary conditions
Table (3) summarize boundary conditions:
Cases Orientation
Air supply
ACH (kg/s)
Air velocity
(m/s)
Gross area
Agross
(m2
)
Air temp.
supply
(ºC)
Air temp.
return
(ºC)
Case 1
Eastern, southern and
ceiling walls
5.0 (0.0768) 0.35 1.1 × 0.53 15 24Case 2 Southern and ceiling wall
Case 3
Southern, western and
ceiling wall
University of Kufa
College of Engineering
Mechanical Eng. Dept.

5. Simulation results
E
W
N
S
Fig. (1) Configuration of the displacement
ventilation test case.
Fig. (2) The positions of the measuring
poles for the displacement ventilation
test case.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

6. a a
b b
Fig. (3) Distribution of calculation air temperature contours
with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (4) Distribution of calculation air temperature contours
with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

7. a a
b b
Fig. (5) Distribution of calculation air temperature contours
with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (6) Distribution of calculation air temperature contours
with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

8. a a
b b
a
Fig. (7) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (8) Distribution of calculation air temperature contours
with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

9. a a
b b
Fig. (9) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (10) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

10. a a
b b
Fig. (11) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (12) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

11. a a
b b
Fig. (14) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (15) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

12. Fig. (16) Effect draft temperature for k-ε and
k-ω models, (a) case1, (b) case 2, (c) case
3.
a b
c

13. Grille Diffuser
Boundary conditions:
Supply diffuser: mass flow rate of 0.0768 kg/s , turbulence intensity of 4% .
Return: The outlet is specified as pressure outlet.
Thermal conditions:
• Computer 1: 171.43 W/m2
• Computer 2: 274.6 W/m2
• Human simulators: 41.9 W/m2
• Lamps: 37.78 W/m2
Turbulence modeling: Applying that the Realizable k-ε and the SST k-ω models.
Computation meshes: (499,952) cells.
Numerical schemes: discretized using the second-order upwind scheme. For the discretization of
pressure, the PRESTO! (PREssure STaggering Option) scheme is used. The SIMPLEC scheme is used
for the pressure-velocity coupling.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

14. Summary of boundary conditions
Table (4) summarize boundary conditions:
Cases Orientation
Air supply
ACH (kg/s)
Air velocity
(m/s)
Gross area
Agross
(m2
)
Air temp.
supply
(ºC)
Air temp.
return
(ºC)
Case 1
Eastern, southern and
ceiling walls
5.0 (0.0768) 2.7 0.28 × 0.18 15 24Case 2 Southern and ceiling wall
Case 3
Southern, western and
ceiling wall
University of Kufa
College of Engineering
Mechanical Eng. Dept.

15. Simulation results
Fig. (17) Configuration of grille ventilation
test case
Fig. (18) The positions of the measuring
poles for the grille ventilation test case [13].
E
W
N
S
University of Kufa
College of Engineering
Mechanical Eng. Dept.

16. a a
b b
Fig. (19) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (20) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

17. a a
b b
Fig. (21) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (22) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

18. a a
b b
Fig. (23) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (24) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

19. a a
b b
Fig. (25) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (26) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

20. a a
b b
Fig. (27) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (28) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

21. a a
b b
Fig. (29) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (30) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

22. a b
c
Fig. (31) Grille effect draft temperature for k-ε
and k-ω models, (a) case1, (b) case 2, (c)
case 3.

23. Slot Diffuser
Boundary conditions:
Supply diffuser: mass flow rate of 0.1410 kg/s , turbulence intensity of 5% .
Return: The outlet is specified as pressure outlet.
Thermal conditions:
• Computer 1: 171.43 W/m2
• Computer 2: 274.6 W/m2
• Human simulators: 41.9 W/m2
• Lamps: 37.78 W/m2
Turbulence modeling: Applying that the Realizable k-ε and the SST k-ω models.
Computation meshes: (1,071,118) cells.
Numerical schemes: discretized using the second-order upwind scheme. For the discretization of
pressure, the PRESTO! (PREssure STaggering Option) scheme is used. The SIMPLEC scheme is used
for the pressure-velocity coupling.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

24. Summary of boundary conditions
Table (5) summarize boundary conditions:
Cases Orientation
Air supply
ACH (kg/s)
Air velocity
(m/s)
Gross area
Agross
(m2
)
Air temp.
supply
(ºC)
Air temp.
return
(ºC)
Case 1
Eastern, southern and
ceiling walls
9.2 (0.1410) 3.9 1.15 × 0.10 15 24Case 2 Southern and ceiling wall
Case 3
Southern, western and
ceiling wall
University of Kufa
College of Engineering
Mechanical Eng. Dept.

25. Simulation results
Fig. (32) Configuration of slot ventilation
test case.
Fig. (33) The positions of the measuring
poles for the ceiling slot ventilation test
case, [13].
E
W
N
S
University of Kufa
College of Engineering
Mechanical Eng. Dept.

26. a a
b b
Fig. (34) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m
Fig. (35) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m

27. a a
b b
Fig. (36) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m
Fig. (37) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m

28. a a
b b
Fig. (38) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (39) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

29. a a
b b
Fig. (40) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (41) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

30. a a
b b
Fig. (42) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (43) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

31. a a
b b
Fig. (44) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (45) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.

32. a b
c
Fig. (46) Slot effect draft temperature
for k-ε and k-ω models, (a) case1, (b)
case 2, (c) case 3.

33. Square Diffuser
Boundary conditions:
Supply diffuser: mass flow rate of 0.750 kg/s , turbulence intensity of 5% .
Return: The outlet is specified as pressure outlet.
Thermal conditions:
• Computer 1: 171.43 W/m2
• Computer 2: 274.6 W/m2
• Human simulators: 41.9 W/m2
• Lamps: 37.78 W/m2
Turbulence modeling: Applying that the Realizable k-ε and the SST k-ω models.
Computation meshes: (1,751,500) cells.
Numerical schemes: discretized using the second-order upwind scheme. For the discretization of
pressure, the PRESTO! (PREssure STaggering Option) scheme is used. The SIMPLEC scheme is used
for the pressure-velocity coupling.
University of Kufa
College of Engineering
Mechanical Eng. Dept.

34. Summary of boundary conditions
Table (6) summarize boundary conditions:
Cases Orientation
Air supply
ACH (kg/s)
Air velocity
(m/s)
Gross area
Agross
(m2
)
Air temp.
supply
(ºC)
Air temp.
return
(ºC)
Case 1
Eastern, southern and
ceiling walls
4.9 (0.750) 5.2 0.3 × 0.3 15 24Case 2 Southern and ceiling wall
Case 3
Southern, western and
ceiling wall
University of Kufa
College of Engineering
Mechanical Eng. Dept.

35. Simulation results
Fig. (47) Configuration of ceiling slot
ventilation test case.
Fig. (48) The positions of the measuring
poles for the ceiling slot ventilation test
case, [13].
E
W
N
S
Fig. (49) modeling of the square diffuser.

36. a a
b b
Fig. (50) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (51) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

37. a a
b b
Fig. (52) Distribution of calculation air temperature
contours with k-ε , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (53) Distribution of calculation air temperature
contours with k-ω , case 1,
(a) plane at z=1.825m, (b) plane at z=0.4m.

38. a a
b b
Fig. (54) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (55) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

39. a a
b b
Fig. (56) Distribution of calculation air temperature
contours with k-ε , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (57) Distribution of calculation air temperature
contours with k-ω , case 2,
(a) plane at z=1.825m, (b) plane at z=0.4m.

40. a a
b b
Fig. (58) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (59) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4 m.

41. a a
b b
Fig. (60) Distribution of calculation air temperature
contours with k-ε , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4m.
Fig. (61) Distribution of calculation air temperature
contours with k-ω , case 3,
(a) plane at z=1.825m, (b) plane at z=0.4 m.

42. a b
c
Fig. (62) Slot effect draft temperature
for k-ε and k-ω models, (a) case1, (b)
case 2, (c) case 3.