ZEMCH 2019 International Conference Proceedings April.2020 | Page 287
1.2.1 Hydronic Radiator (HR)
Petr Ovchinnikov et al [5] made a study that aims at evaluating practical application of low
temperature hydronic space heating systems in residential buildings in Russia. M. Jangsten et al [6]
stated that in order to maintain the competitiveness and improve the environmental performance of
district heating. In the future, it is essential to transition to lower operating temperatures and suggested
supply and return temperatures of 50–55 °C and 20–30 °C for low temperature radiators.
1.2.2. Radiator‐Convector (RC)
Jonn Are Myhren and Sture Holmberg [7] used a ventilation radiator i.e., a combined ventilation
and heat emission unit to increase energy efficiency in exhaust‐ventilated buildings with warm water
heating. They validated the results achieved by Computational Fluid Dynamics on the heat transfer
from internal convection fins, and presented results which showed the heat output of ventilation
radiators may be improved by at least 20% without sacrificing ventilation efficiency or thermal comfort.
Improved thermal efficiency of ventilation radiators allows a lower supply water temperature and
energy savings both for heating up and distribution of warm water.
Adnan Ploskić, and Sture Holmberg [8] showed that the proposed air‐heater was able to lift the
temperature of supply air at 10 l/s from −15 °C to 18.7 °C using 40 °C water supply. In addition, a
thermal performance analysis showed that radiator systems equipped with the proposed air‐heater
could meet a space heat loss of 35.6 W per square meter floor area, using supply water of 40 °C
Arefeh Hesaraki et al [9] concluded that the mean supply water temperature for floor heating of
30 °C was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements
for conventional radiator was significantly namely, 45 °C. Experimental results indicated that the mean
indoor temperature was close to the acceptable level of 22 °C in all cases.
Adnan Ploskić et al [10] found that staggered convector plates was more efficient in preheating the
incoming outdoor air supply. With this plate design, the evaluated radiator increased the temperature
of the incoming airflow of 10 l/s from ‐5 °C to 26 °C with water supply/return temperatures of
45 °C/35 °C. With these water temperatures, the radiator was able to cover a room heat loss of 34 W/m2
floor area. However, the design of the convector plate alone was found to have a limited impact on the
heat output from the radiator
2. Materials and Methods
2.1 HR and vertical ground heat exchanger.
Ooi and Masa [11] showed by simulation that the circulation of water in a 400m‐deep 25mm‐
diameter U‐tube, i.e., a vertical ground heat exchanger (VGHE) shown in Figure 2 (L) to hydronic
radiators on opposite long walls could heat a 60m2 Melbourne, Australia house, energy‐rated to the
mandatory 6 stars, to the Nationwide House Energy Rating (NatHERS) respective day and night
heating thermostats of 20°C and 15°C.
Figure 2 (center) shows that this 400m‐depth is derived from the 17°C recorded at 50m depth, and
a linear increase of 2°C above the annual average outdoor temperature of 15°C. The average
temperature surrounding the 400m deep U‐tube is then 23°C, hot enough for the daytime heating
thermostat of 20°C. The heat extracted from the ground in winter can be replenished during summer
using solar‐heated water, thus this deep ground is a constant temperature store and renewable heat
source.
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