Page 37 - Kỷ yếu hội thảo quốc tế: Ứng dụng công nghệ mới trong công trình xanh - lần thứ 9 (ATiGB 2024)

28 TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT - ĐẠI HỌC ĐÀ NẴNG

V is the air flow rate (m/s);  and ki are the In which, mkk (kg/s), Ckk (J/kg.K) are the flow rate
o
i and specific heat capacity of air, respectively; t0 ( C),
thickness and heat transfer coefficient of the glass and tcomf ( C) are the initial temperature in the cabin and the
o
car body shell (m), respectively [6]. required comfortable temperature in cabin,
5) The Heat Emitted from the Engine respectively;  (s) is the time required to reach the the
p
This heat emitted from the engine would affect the comfortable temperature.
cabin temperature. The heat emitted from the engine
was determined according to the equation below [13]. C. Calculation and Simulation Programming
Method
Q F . h ( . t − t ) (10)
=
eng eng cabin eng in The programming for calculation and simulation of
thermal loads applied to cabin was conducted on
In which, F is the outer surface area of the Matlab 2022 software. The algorithms on matlab were
eng
based on the equations for calculating thermal loads
engine (m ); t and t are the engine temperature and applied to cabin. The calculation programming using
2
eng in
the ambient temperature in the cabin ( C), functions, which were available in the Matlab library
o
respectively. Engine temperature is determined to calculate and display the value of the thermal loads
according to the following empirical equation [10]. such as: heat emitted from humans, and radiation heat.
The thermal loads such as heat exchanged with the
6
t 2.10 RPM 2 air, heat emitted from the engine, and heat loss due to
−
=
−
eng (11)
+ 0.0355RPM + 77.5 ventilation have changed continuously during the heat
exchange process with the air in the vehicle cabin.
6) The Heat Loss Due to Ventilation These parameters were programmed and simulated
The heat loss due to ventilation between the cabin based on the heat transfer law, in which, the heat
and environment depends on the thermal and humidity transfer partial equation, the initial conditions and
parameters of the air outside the environment and in boundary conditions of the heat transfer problem were
the cabin. The heat loss was determined by the determined. The heat transfer equations were solved
following equation [6]. based on the finite difference method on Matlab 2022
software [12]. In the heat-transfer function, the PDEs
Q = m (i − i ) (12) (partial differential equations) problem was solved by
ven ven kk in
pdepe function which was available in the Matlab
In which, mven is the circulating air flow (kg/s); ikk library and was adjusted and complemented.
and iin are the enthalpy of air outside the environment The heat transfer partial equation, the initial
and in the cabin. They were determined according to conditions and boundary conditions of the heat
the following equation [17]: transfer problem of thermal loads applied to cabin
)
6
+
i = ( 2.501.10 1770t X (13) were presented as the equations below [13].
1006 t +
+ The heat transfer partial equation
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Where t ( C) is the temperature of air and X (%) is 2
the relative humidity of the air. t  = 1   t (15)
The heat emitted from the exhaust gas was    C p x  2
considered insignificantly, when the exhaust gas
system was separated under the car's chassis. + The initial condition
7) The Cooling Capacity of the Air Conditioning t x, t (16)
( ) 0 =
System of the Vehicle 0
The cooling capacity of the air conditioning system + The boundary condition
depends on parameters such as total heat applied to
cabin, required comfortable temperature in cabin and t 
the time needed to reach the comfortable temperature. −  x  =  ( t − ) t (17)
a
The cooling capacity was determined according to the x x s x x
s
following empirical equation [16]. In which, ρ (kg/m ), Cp (kJ/kg. C), α (W/m . C)
3
o
2 o
Q = Q + ( m .C 5600+ ) are density, specific heat, and convective heat
0 tot kk kk exchange coefficient of air, respectively
   (14) λ (W/m. C) is thermal conductivity coefficient of
o
( t − t comf ) / ...  p   glass or body shell of vehicle.
0
 ln t − t comf 
0
ISBN: 978-604-80-9779-0