Experimental comparison of zone cooling load between radiant and air systems

Abstract

(Jingjuan (Dove) Feng) Highlights We experimentally compared cooling loads between radiant and air systems  Radiant system has on average 18%-21% higher cooling rates compared to air system  A new definition must be used for radiant system cooling load  HB approach should be used for radiant system cooling load calculation  RTS or weighting factor methods may lead to incorrect results for radiant systems AbstractRadiant cooling systems work fundamentally differently from air systems by taking advantage of both radiant and convective heat transfer to remove space heat. This paper presents an experiment investigating how the dynamic heat transfer in rooms conditioned by a radiant system is different from an air system, and how such differences affect the sensible cooling load and cooling load calculation methods for radiant systems. Four tests with two heat gain profiles were carried out in a standard climatic chamber. For each profile, two separate tests were carried out to maintain a constant operative temperature: one with radiant chilled ceiling panels; and a second with an overhead mixing air distribution system. Concrete blocks were used to create a thermal mass effect. The experiments show that, during the periods the heat gain was on, the radiant system has on average 18%-21% higher instantaneous cooling rates compared to the air system, and 75-82% of total heat gains were removed, while for the air system only 61-63% were removed. Based on the study, we conclude that a new definition must be used for radiant system cooling load, which should be characterized as the combined radiant and convective heat removal at the cooled surface. Calibrated dynamic energy simulation based on a fundamental heat balance approach showed good accuracy. Simplified cooling load calculation methods, such as RTS or weighting factor method, may lead to incorrect results for radiant systems.

Thermal Ceramic Panels and Passive Systems in Mediterranean Housing: Energy Savings and Environmental Impacts

“…Previous research shows that when using conditioning systems by radiant surfaces by capillary tube mats in false removable ceilings, annual energy demand of office buildings located in continental climatic zones, can be up to 30% lower, consequently reducing environmental impacts [11,22,24,45]. The most important reasons were explained in Section 3.…”

“…This significant difference with convective systems (radiators) in winter, and forced air solutions in summer, leads to considerable improvements in comfort and energy savings [11,22]. Peaks in thermal loads are significantly reduced, sensation of comfort is improved with moderate and homogeneous temperatures, and air velocity is imperceptible by body sensors, while people's health is preserved in the absence of excessively cold focal points [9,23,24]. Furthermore, the sound level is imperceptible as air is moved only to dehumidify (very low flow rates), and the presence of dust or bacteria in the ambient air is reduced.…”

Potential Research Areas in Residential Energy Storage for NIST’s Engineering Laboratory

“…PCM plates with polystyrene insulation can be used below the floor instead of tubing (Sharma et al, 2009). Feng et al (2013) measured the performance of radiant cooling panels in an environmental chamber. EL has the capabilities for conducting similar studies using its environmental chambers.…”

Method to Integrate Radiant Cooling with Hybrid Ventilation to Improve Energy Efficiency and Avoid Condensation in Hot, Humid Environments

“…Regarding the PMV as well as the Adaptive Comfort models, the outputs of the tools indicate that the condition of the room was in the comfort zone. The comfort level was enhanced by increasing air velocity in the PMV model [40,41]. Up to certain limits, the incorporation of fans or increasing the speed of the air intake from the mechanical ventilation outlet will help improve thermal sensation by increased room temperature.…”