ASHRAE Journal - November 2019 - 56

TECHNICAL FEATURE

Literature Review
By the end of the past century, Stetiu and Feustel (1995)
developed a model that could accurately simulate the
dynamic performance of hydronic radiant cooling.
Substantial research was also conducted on radiant
cooling by the early years of this century. Zmrhal et al.
(2003) carried out experimental and CFD simulation studies to investigate indoor climate and thermal
comfort in a space cooled by a radiant cooling ceiling,
whereas Jeong and Mumma (2004), developed a simplified correlation for estimating the cooling capacity for a
top-insulated metal ceiling radiant cooling panel. This
was done by statistically analyzing the impact of various
panel design parameters on the panel's cooling capacity
and using linear regression to develop the correlation.
A different approach was adopted by Ma and Sunaga
(2004), who studied the thermal performance of radiant
cooling with on-roof water flow, using the evaporative
cooling effect on the roof surface. The thermal performance of that system was examined experimentally
using a test house. A similar study was done by Vangtook
and Chirarattananon (2006), who presented both an
experimental and simulated study of the application of
radiant cooling using natural air for ventilation under
the hot and humid climate conditions of Thailand. A
similar study was carried out by Tantiwichien (2006) on
the use of radiant cooling panels by applying the cool
water coming directly from the cooling tower to the
radiant cooling panel under the weather conditions of
This paper was first presented at the 2018 ASHRAE Winter
Conference.
56

ASHRAE JOURNAL

ashrae.org

N O V E M B E R 2 0 19

FIGURE 1 Temperature results of validation test case.

Normalized Temperature T/TRP

comparing its output to the experimental data available
in the literature.
2. Investigate airflow patterns, velocity profiles,
temperature distribution, and comfort indices inside
a cleanroom, which is a measurement laboratory and
meant to be cooled with the following proposed arrangements:
* Radiant cooling with radiant panels installed on the
ceiling
* Radiant cooling with radiant panels installed on the
walls
* Conventional convection cooling
3. Compare the performance of the three proposed arrangements and define the arrangement that best suits
the application of a cleanroom.

1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0

Experiment
Modeling
0

30
40
50 60
70
80
Normalized Vertical Distance Z/H (%)

100

the southern part of Thailand. Focusing on cleanroom
applications, Memarzadeh (2007) discussed a ventilation strategy utilizing ceiling exhausts only, a combination of ceiling exhausts and bench exhausts, and ceiling
radiant-cooling panels in a typical laboratory using
CFD simulation. Recently, Catalina and Virgone (2007),
studied, experimentally and using CFD simulation, the
thermal performance and the thermal comfort inside a
test room called "Minibat" with a radiant ceiling panel
using capillary tubes.

Software Validation
To validate the CFD software used in this study, experimental data from the work by Catalina and Virgone
(2007) were used to examine the K- e model. The test
case involved a room that was air-conditioned via a
radiant ceiling panel. The temperature of the thermal
guard placed on the ceiling was set to 26°C (78.8°F) for
the duration of the experiment. It was observed that
there were variations at a maximum of 1°C (1.8°F) due
to the system controller, which were considered acceptable. Figure 1 shows the predicted temperature curves,
normalized by the radiant panel temperature, for values
obtained in the center of the test cell along the z direction as well as the experimental measurements. It shows
that temperature field predictions by the CFD code
are in agreement with the experimental and numerical results. The figure shows that the numerical results
errors obtained by the CFD code are within 6% to 8%
of the experimental measurements. This deviation is
caused by the values of air absorptivity per unit length a
and scattering coefficient s. These coefficients are hard
to define and measure. The coefficients are a function
of the moisture content and relative humidity as well
as the amount of pollutants and aerosols in the air. In
the current study, both coefficients are set to zero. This

ASHRAE Journal - November 2019

Table of Contents for the Digital Edition of ASHRAE Journal - November 2019