Soğuk depo modelinin deneysel ve 3 boyutlu sayısal analizi
Öz
Soğutma sanayinde sıcaklık ve nem kontrolü büyük önem taşımaktadır. Laboratuvar ortamında yapılan
çalışmalar maliyet artışı ve zaman kaybına neden olduğu için sayısal analiz programları ile bu sorunun
çözülmesi amaçlanmaktadır. Bu çalışmada, deney ortamında içi boş bir soğuk hava deposu kullanılarak
sıcaklık ve hava dolanım hız verileri ile sayısal analiz programı ölçüm sonuçlarının karşılaştırılması
amaçlanmıştır. Soğuk hava deposu ortam sıcaklığından set aralık değeri 275.15 K - 272.95 K olan değere
inilip hız ve sıcaklık değerleri datalogger kullanılarak alınmıştır. Sayısal analiz için öncelikle hava akışının
olacağı kabin üç boyutlu olarak modellenmiş ve ağ yapısı sonlu elemanlar yöntemi kullanılarak
oluşturulmuştur. Tüm deney şartları hesaplamalı akışkanlar dinamiği hava akış simülasyon yazılım
programı zamana bağlı olarak tanımlanıp deney sonuçlarıyla karşılaştırılmıştır. Sonunda deney ile yazılım
programı arasında yakınsama görülmüştür. Sonuçların yakınsamasından dolayı 3 farklı fan hızı içinde
programı çalıştırılmıştır. Kabin içindeki hız ve basınç dağılımları akış çizgileri, vektörler ve eş büyüklük
eğrileri şeklinde grafik olarak gösterilmiştir. Alınan sıcaklık, basınç ve hız değerleri yorumlanmıştır.
Anahtar Kelimeler
Experimental and 3D numerical analysis of a cold store model
Abstract
Temperature and humidity control are vital in the
cooling industry. As laboratory works cause
increased costs and loss of time, the study aims at
solving this problem by numerical analysis software.
This study has aimed to compare the temperature
and air-circulation rate data with numerical
analysis software measurement results using an
empty cold room in an experimental environment.
The cold room temperature has been dropped to the
set range value of 275.15 K to 272.95 K and
temperature and air velocity values have been
obtained using a datalogger. For numerical
analysis, first, the cabin where the airflow will occur
has been modeled as 3D and the network structure
has been formed using a finite elements method. All
experimental conditions have been defined timedependently
by the Computational Fluid Dynamics
(CFD) airflow simulation software and compared
with the experiment results.
A convergence has been seen between the
experiment and the software. CFD software has
been started under 3 different fan rates due to the
convergence of the results. Rate and pressure
distributions inside the cabin have been shown in a
graph with flow lines, vectors, and isosize curves.
Values of temperature, pressure and velocity have
been interpreted.
There are two basic approaches in the design and
analysis of engineering systems. These are
calculation and experimentation. The results of
calculation must tested experimentally. Today,
designers use both experimental and CFD analyses,
because these two different methods complete each
other. While general characteristics such as
pressure, temperature, velocity can measured
experimentally, detailed properties such as shear
stresses, velocity distributions, temperature and
pressure distributions and flow lines can calculate
using experimental data.
One of the most effective numerical methods, which
allow the use of differential equations in order to
construct mathematical models and to solve these
equations by means of computer software is the
finite elements method. The method is based on the
formation while expressing the system
characteristics of an element, and then a linear
equations set by combining the equations formed for
each element to express the whole system. The finite
element method, which is capable of solving all
complicated problems such as various boundary
conditions, time dependent linear and non-linear
problems rapidly spread in application and
theoretical scientific fields in the last half-century
An important point to note is that even though a fine
mesh provides a better solution, since the physical
refinement of the solution always depends on the
physical refinement of the model, details were
ignored in the model.
In cold store, velocity control of temperature and air
circulations carried as much importance as humidity
control. Many parameters should be evaluated
together for this aim and the most appropriate
conditions should be met. In this study, ventilator
velocity, ventilator position, product storage type,
evaporator surface areas, working times of systems
and pressure distribution inside cabin were
evaluated separately.
High air movement is desiccated fresh products.
On the other hand, very slow air movement causes
freeze of humidity inside the cooling unit. Therefore,
air velocity must kept within the limits by sufficient
for product quality. Relative humidity in cold store
depends on storage temperature, air flow rate,
evaporator surface areas, number of ventilators, and
cross sectional areas of ventilators.
With the method used in this study, air circulation
velocity and storage temperature can select for all
products. In this way, by definition of time
dependent boundary conditions, CFD simulations
achieved. Many parameters such as ventilator
position, air velocity, temperature distribution inside
the cabin. can monitored easily according to
storage conditions.
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