Radiant Heating System Research Articles

Parametric study on the effect of radiant heating system on indoor thermal comfort with/without external thermal disturbance

For radiant heating system, less concern has been given to the fact that supply water temperatures are determined according to local conditions, and it is unclear how surface emissivity of the system affects indoor thermal comfort. Therefore, the application of radiant heating system with fixed water supply temperature in two different types of buildings is analyzed. The transient simulation is verified experimentally and the results show that when the radiator area is determined, adjusting water supply temperature has a great effect on thermal comfort. Changing the basic water temperature by 5 °C can reduce the thermal comfort by 20%. Therefore, it is more reasonable to determine the water supply temperature first and then design other parameters, which can improve thermal comfort and reduce unnecessary energy consumption. The radiator surface emissivity changes thermal comfort mainly by affecting the response speed. The higher the emissivity, the better the thermal comfort. However, if only considering the acceptable thermal comfort zone, changing the emissivity will have little effect on thermal comfort. The time proportion of acceptable thermal comfort zone is only reduced by 5% when emissivity changes from 0.95 to 0.5. Therefore, users can choose radiator surface materials more flexibly according to their needs.

Performance optimization of a sidewall radiant heating system integrated with diffuse ceiling ventilation

Radiant heating systems typically created a non-uniform thermal environment. The effect of radiant asymmetry on human thermal comfort was the main consideration in its application. However, previous studies did not emphasize the method of supplying fresh air and its impact on the asymmetric thermal environment. In this study, flow field distribution in a radiant heating room with diffuse ceiling ventilation system which had different porous ceiling opening rates was studied by numerical simulations. Meanwhile, subjective experiments were conducted to evaluate the influence on human thermal comfort. The results revealed that under different porous ceiling opening rates, non-uniform opening on the porous ceiling could optimize the indoor asymmetric thermal environment and reduce local draft discomfort. Furthermore, the neutral level in the room could be maintained at the same height by adjusting ceiling opening rates. The method of supplying fresh air into the radiant heating room had a certain impact on the asymmetric thermal environment. This paper served as a reference for the future design of the radiant system combined with a fresh air system.

Experimental and Numerical Study on Thermal Performance of a Novel Direct Expansion Air-Source Heat Pump Heating System

In this paper, a novel direct expansion air-source heat pump heating system with a gravity-driven radiator as a heating terminal was developed, for the purpose of reducing the energy consumption and improving the thermal comfort of indoor personnel. The thermal response speed of the system at the start-up stage was experimentally studied firstly. The results showed that the thermal response speed of the developed system was slightly lower than that of a traditional air-source heat pump heating system with a convective heating terminal, but largely higher than that of an air-source heat pump floor radiant heating system. When the outdoor air temperature fluctuated between −5.2℃ and −1.0℃, the average rising ratios of indoor air temperature at the start-up stage for the developed heating system and the traditional system are 10.8℃/h and 13.8℃/h respectively. On this basis, an optimization study was then conducted to further improve the thermal performance of the developed heating system. The numerical results indicated that integrating a cross-flow fan to the gravity-driven radiator is able to promote the thermal performance of the heating system obviously at the start-up stage, because the convection heat transfer of the radiator was highly enhanced. Among the simulation conditions, the time required for the air temperature at head height to reach the designed temperature is shortest when the flow angle of the fan is 0° with an air speed of 0.6 m/s. while setting the flow angle of the fan to −45° with an air speed of 0.4 m/s is recommended to achieve the most thermal comfort for the whole body.

Integrated effects of the heat recovery ventilation and heat source on decay rate of indoor airborne particles: A comparative study

Given the high concentration of indoor airborne particles during the winter and their harmful effects on human health, it is of great importance to examine combined effects of the ventilation and heat source on indoor particle dispersion. The present study aims to investigate transient dispersion and deposition of indoor particles under the heat recovery ventilation (HRV). Five groups of particles with different diameters ranging from 0.1 to 10 μm were taken into account, representing the inhalable indoor airborne particles. By considering three different heating systems, including the radiator, floor heating system and fan coil, the integrated ventilation-heating effects on particle dispersion were evaluated and compared. An Eulerian-Lagrangian CFD model was developed to predict turbulent characteristics of the airflow field and unsteady particle trajectories. The role of particle size, air change rate and outdoor temperature was addressed. In addition, influence of the heat source position on the particle decay rate and removal efficiency was investigated. The results indicated that the impact of heating system on the particle decay rate is weakened by increasing the ventilation rate. Among all heating systems, the radiator renders the highest dispersion rate and the slowest decay rate, even lower than a single HRV unit. It was revealed that, for an intermediate ventilation rate, the particle deposition rate in fan coil system is 3.6 and 2.4 times faster than the radiator and floor heating systems, respectively. It was also found that displacing the radiator to the opposite side of the ventilation unit quadruplicates the removal efficiency and leads to 146% enhancement of the decay rate coefficient.

A thermal-hydraulic coupled simulation approach for the temperature and flow rate control strategy evaluation of the multi-room radiator heating system

The lack of efficient temperature and flow rate control strategy is one of the key factors in excessive energy consumption of the district heating (DH) system. The current researches on secondary network simulation and control usually tackle the hydraulic characteristics of the network and building thermal dynamic separately. However, for the multi-room radiator heating system, the hydraulic characteristics and building thermal dynamics are coupled. An effective coupled thermal-hydraulic model for simulation and control of multi-room radiator heating systems is essential. In this paper, a novel thermal-hydraulic coupled simulation approach is proposed. The temperature distribution and thermal capacity of the radiator, as well as the hydraulic characteristics of the radiator heating network, are considered. A numerical method is developed to solve the proposed model. Different control strategies are analyzed based on the model. Result shows that efficient terminal flow rate control can save 8.4%–13% energy. The proportional control is superior to the on-off control in maintaining indoor temperature, while their energy consumptions are the same. Additionally, the hydraulic coupling effect of the network between households and floors should be considered if the balance valves are not installed on each floor.

Decentralized heat supply systems for industrial buildings using natural gas from the Arctic zone

The article discusses the issue of saving fuel resources, a significant reduction in the cost of maintaining and purchasing gas high-temperature sources of heat supply. The paper proposes for comparison a radiation heating system and a system with a water coolant, taking into account the design features of production shops. This assessment was carried out for an industrial facility to be located in Novy Urengoy, Yamalo-Nenets Autonomous Okrug, Russia.

Mock-Up Test on the Application of Phase Change Materials in Underfloor Radiant Heating System in Apartments

Mock-Up Test on the Application of Phase Change Materials in Underfloor Radiant Heating System in Apartments

발열유리 창호시스템의 발열량에 따른 실내공간 열적 쾌적성능 분석

Purpose: In this study, an approach using the heated glazing window system as an auxiliary heating system is evaluated in terms of thermal comfort. Heat loss through window parts can occur relatively high because of low thermal resistance, which causes keeping lower surface temperature of the window, typically when outdoor air temperature is lower. With such issues, occupants may feel thermal discomfort near window parts mainly due to the radiant temperature asymmetry. In this study, an approach using the heated glazing window system as an auxiliary heating system is proposed to improve the performance of occupant‘s thermal comfort in a conditioned room. Method: For this analysis, a floor radiant heating system is considered as the main heat supply system in the conditioned zone. The internal thermal information of the room is calculated using a two-dimensional heat transfer analysis simulation (i.e., TRISCO). To quantitatively analyize the thermal comfort of the space adjacent to the window, the Predicted Mean Vote(PMV) at each point is derived by dividing the internal space into a two-dimensional grid. Result: As a result of the analysis, it was found that the heated glazing window system contributes to making the indoor thermal comfort uniform and can improve the thermal comfort of the window adjacent area. The maximum PPD deviation of the indoor space is about 6.3% when the heated glazing system is not operated, 1.8% under the heating of 20W/㎡, and 0.08% under the heating of 40W/㎡

Development of diatomite-based shape-stabilized composite phase change material for use in floor radiant heating

The utilization of phase change materials (PCMs) in floor radiant heating system can reduce energy consumption along with enhancing thermal comfort by reducing indoor temperature fluctuations. However, the leakage and poor thermal performance of PCM limit its further applications. Here, to solve the above problems, sodium acetate trihydrate (SAT)-acetamide (AC)-micron/nano aluminum nitride (AlN) composite phase change material (CPCM) was composited with heat-treated diatomite to prepare diatomite-based shape-stabilized CPCM (SSCPCM) for use in floor radiant heating. The effect of treating temperature on diatomite’s porous structure was analyzed by porosity analyzer to determine the optimal heat-treated diatomite as supporting material. Subsequently, the effects of the mass fraction of diatomite on phase change properties, and shape-stabilized ability of diatomite-based SSCPCM were investigated. Meanwhile, the morphology, chemical compatibility analysis and thermal properties of SSCPCM were discussed in detail. Results indicated that diatomite calcined at 400 °C had large surface area and high porosity, giving it good adsorptive capacity for SAT-AC-AlN CPCM. SSCPCM with 37.5 wt% diatomite had a good shape stability, which melted at 46.5 °C with high latent heat of 162.5 kJ/kg, low supercooling degree of 0.33 °C and good thermal stability and thermal reliability, making it prospective potential in floor radiant heating.

Performance of air and ground source heat pumps retrofitted to radiator heating systems and measures to reduce space heating temperatures in existing buildings

Heat pumps are expected to play a central role in decarbonizing heat supply, but face challenges in existing buildings due to high temperature requirements of existing radiator systems. This paper links the performance analysis of heat pump systems with methods to reduce temperatures of the space heating circuit. Field data and system simulations of air and ground source heat pumps show a linear correlation between the seasonal performance factor SPF and the mean heat pump temperature over a wide temperature range. Every Kelvin of reduced heat pump temperature increases the SPF by 0.10–0.13 points. Applied methods to reduce heating temperatures are demonstrated at existing multi-family buildings. Thermal insulation reduces the building's heat load, allowing a reduction of heating temperatures with the existing radiators. A further temperature reduction is achieved by analyzing the required heating power per room and identifying critical, undersized radiators. In a studied building, the selective exchange of only 7% of all radiators is sufficient to reduce heating temperatures from 75 °C/60 °C–55 °C/45 °C. This corresponds to a reduction of the electricity consumption by 40–42%. However, the potential of these methods is specific for each building and depends particularly on its renovation state and installed radiator capacity. Nonetheless, an energy- and cost-efficient operation of heat pumps retrofitted in existing radiator heating systems is viable, if following the proposed system design method linking heat pump performance and reduction of space heating temperatures.

Optical Model of Thermal Radiation Loading System for Turbine Vane Leading Edge

With the increase of combustion temperatures, the thermal radiation effect for hot components in the new generation of aero-engines has become a key factor in the combustion process, cooling structure design, and thermal protection. A radiation loading system can be used as an external heat source to simulate the real thermal environment of hot components in aero-engines. Total receiving power, as well as 3-D heat flux distribution, should better coincide with real conditions. With the aid of freeform optics and the feedback optimization method, the current study develops a concentrating-type radiation heating system fit for the leading-edge surface of a C3X turbine vane. A xenon lamp combined with a freeform reflector was optimized for controllable heat flux. A design method in the area of illumination engineering was innovatively extended for the current model. Considering the effect of polar angular radiative flux distribution of a xenon lamp, a Monte Carlo ray tracing (MCRT) method was adopted to evaluate the optical performance. Feedback modifications based on Bayesian theory were adopted to obtain the optimal shape of the FFS for target heat flux. The current study seeks a feasible way to generate 3-D heat flux distribution for complex curved surfaces, such as turbine vane surfaces, and helps to simulate the real thermal environment of hot components in aero-engines.

Reducing energy capacity and increasing the environmental safety of industrial areas when using radiative heating systems based on water infrared radiators

Introduction. It has been repeatedly proven that the use of radiant heating systems leads to an increase in the environmental safety of industrial premises by increasing their energy efficiency. The most promising solution is the use of gas infrared emitters, in which there is no intermediate coolant, and the heat of combustion of the gas enters the room. However, such a solution has a number of limitations on gas availability, comfort and fire hazard. Also, a highly efficient solution is the use of water infrared emitters, which can be represented by emitting panels or emitting profiles that use an intermediate coolant, but do not have many limitations inherent in gas systems.
 
 Materials and methods. This study was conducted in the Laboratory of radiant Heating of NNGASU and is devoted to the study of the peculiarities of the formation of the temperature regime in rooms heated by water infrared radiators, as well as the thermal regime of external enclosing structures in these rooms.
 
 Results. Based on the results of the experiments, the authors concluded about the formed thermal regime in rooms with heating systems based on water infrared emitters. It is proved that the use of radiant heating leads to a more uniform temperature regime in a heated room, and less overheating of the room covering than when using convective heating systems.
 
 Conclusions. The energy efficiency of the use of radiant heating systems based on water infrared emitters has been proven. The study showed that the system of water radiant heating allows to reduce the gradient of air temperature in height not only in large-volume rooms, such as workshops, depots, gyms, but also in rooms with a low height of the coating location. This feature allows you to reduce heat losses through the coating. The temperature regime in the working area of the room with the use of radiant water heating, in comparison with convective, remains unchanged.

Experimental study on energy consumption and thermal environment of radiant ceiling heating system for different types of rooms

This paper investigates energy consumption and thermal environment performance of a radiant ceiling heating system serving different types of rooms in the same building. Four types of rooms with different functions, namely restaurant, office, flight control room, and conference room, were chosen in this study. Energy consumption and thermal environment parameters were measured in different rooms, including the heating energy consumption intensity, indoor air temperature, surface temperature of the building envelope, air temperature stratification, and vertical temperature gradient. The results show that the heating energy consumption intensity is about 19.63 W/m2, which is about 30% lower than the heating index recommended in the regional standard. The heating indexes per unit area of the restaurant, office, flight control room, and conference room are 33.41, 17.36, 18.91, and 20.32 W/m2, respectively. The unit volume heating energy consumption of the flight control room, which is a large space, is significantly lower than that of the office, which is a small space. Moreover, there are also differences regarding the indoor thermal environment of the different types of rooms. Factors such as solar radiation, outdoor cold air infiltration, and indoor occupancy rate are the main factors that influence the indoor thermal environment. In general, the energy consumption level of radiant ceiling heating systems for larger spaces is lower, and the indoor thermal environment is better. Therefore, radiant ceiling heating systems are more suitable for larger rooms.

Study on Thermal Comfort in Industrial Buildings, Heated by Radiation

This paper is focused on a study between different heating systems commonly used in industrial installations. Industrial heating systems generally raise difficult problems in choosing the most economical system. If several solutions technically meet the requirements of the indoor climate, in terms of energy efficiency we must focus on the optimal solution. The study was conducted to choose the optimal heating solution for an industrial hall, from the point of view of evaluating the efficiency of the installation of an exhaust gas recirculation equipment. The heating of industrial premises generally raises difficult problems due to the diversity of the types of buildings encountered, the variety of activities carried out and the need to choose the most economical system, both in terms of investment and operation. The radiation heating system using natural gas offers the solution of this problem, in situations where the classic heating systems (hot air heating or static bodies) cannot ensure optimal indoor conditions (in the sense that they do not achieve a relatively uniform temperature in the heated space, cause drafts and have low yields). For spaces with a high height (over 4m) these systems can only be considered satisfactory in the case of general heating with very high energy consumption. From the study performed, but also from the specialized technical literature, it is concluded that these systems offer an energy saving, compared to the classical systems.

Field investigations on operational performance of a novel radiant floor heating equipment applied in a typical office building

Low-temperature radiant heating systems are widely used in buildings with significant energy conservation, and they are convenient for the utilization of low-grade energy resources and household metering. In this study, the practical application of a novel radiant floor heating system (RFHS) in cold regions is investigated via construction of an experimental platform for energy consumption and thermal comfort in an office building in Tianjin, China. The results indicated that the novel radiant floor exhibits higher heating capacity and heat transfer coefficient than that of a traditional radiant floor. During the experiment, the average indoor temperature was 25.0°C in the office room and 22.7°C in the conference room, and all instantaneous indoor temperatures exceeded 21°C. To avoid local thermal discomfort, the supply water temperature of the floor can be appropriately decreased by 2–3°C for operation. Additionally, the power consumption of the system is decreased by approximately 11.4% if the indoor temperature is decreased to 20°C. Hence, a 10-h operation mode per day can be adopted in the office building for energy conservation given that the novel radiant floor exhibits superior initial response to intermittent operation. Practical application: In this study, the practical application effect of a new type of water-passing floor is examined in cold regions to provide a design reference for engineering applications. Therefore, it is expected that the results will be helpful to researchers for indoor environments, heating, ventilating, and air conditioning engineers, system manufacturers, and those who want to analyze the operational performance of a radiant floor heating system.

Analysis of Deformation and Stresses of a Lightweight Floor System (LFS) under Thermal Action.

The lightweight floor system (LFS) with a heating coil is one of many types of radiant heating systems. It differs from most of the others, as it has a much higher thermal efficiency at low flow temperature. To verify whether adhesive mortars can safely connect the ceramic floor with the insulating substrate, the deformations and stresses values of all light system layers under thermal action should be checked and compared to their maximum strengths. For this purpose, an LFS test field was conducted using the strain gauges and digital measurement techniques, and floor displacements and deformations were determined. The results obtained from the tests were confirmed by finite element method calculations. It was also found that the stress of each floor component was much lower than their strength. This proves that the LFS with a heating coil, without metal lamellas, meets the safety regulation for use. The results of the analysis can be useful in the design of heated/cooled LFSs.

Applying Solar PV to Heat Pump and Storage Technologies in Australian Houses

Innovative mechanical services coupled with renewable energy systems are crucial for achieving a net zero energy goal for houses. Conventional systems tend to be vastly oversized because they lack the means to buffer energy flows and are based on peak loads. This paper presents an approach to achieve a net zero energy goal for houses by using a solar PV system, heat pumps, and thermal and electrical storage batteries, all off-the-shelf. Constraining one part of the system and then showing how to manage energy storage and flow is a paradigm shift in sizing. The design is for a modest-sized house built in Melbourne, Australia. The output of a solar photovoltaic array drives a small-scale heat pump to heat water, buffering its energy in a thermal battery to energise a radiant space heating system. Space cooling is provided by a separate heat pump. Through energy storage in electrical and thermal batteries, it is possible to meet the electricity, heating and cooling needs of the house for the Melbourne climate with a heat pump that draws less than 1 kW. The design methodology is detailed in an appendix and can be applied to similar projects. This paper contributes to similar work worldwide that aims to reinforce innovative renewable energy driven service design.

A Review of Solar Assisted Radiant Heating System: Experimentation and Simulation Approach

A Review of Solar Assisted Radiant Heating System: Experimentation and Simulation Approach

An experimental investigation on the effect of use of nanofluids in radiant floor heating systems

Hydronic radiant heating systems are widely being run particularly in association with low temperature heat sources. These thermal units are capable of providing high energy saving potential as well as improvement in thermal comfort. Thus, focus on such systems have considerably ascended recently. In this context, augmentation methods have been employed to enhance heat transfer performance of many thermal systems. The use of ultrafine particles in the fluids is considered to be one of the passive techniques, and hence physical properties have been improved compared to the base fluid. Currently, four working fluids’ inlet temperatures are varied from 30 °C to 60 °C, while the mass flow rates are 0.056 and 0.09 kg/s for the heating from floor, and heating from floor along with cooling from walls. Consequently, the examined nanofluids having multi wall carbon nanotube (0.7% vol. cont.) and aluminium oxide (1.26% vol. cont.) have demonstrated better heat transfer performance compared to pure water for similar operating conditions. Nanofluids of greater concentrations such as (0.7% vol. cont.) and (1.26% vol. cont.) have resulted in improvements within the range of 1.7% and 4.9%. Given the improvement in heat transfer acquired, a promising evaluation can be inferred with respect to nanofluids being operated as working fluids in such systems.

Energy Efficiency of Radiant Heating Systems Based on Water-Based Radiant Profiles

It is repeatedly proved that the application of the radiant heating system is cost-effective. The most energy-efficient solution is the use of gas infrared emitters. In this case, there is no intermediate heating medium, and the heat of combustion of the gas enters the premises. However, this solution has a number of restrictions on the availability of natural gas, comfort, and fire hazard. Also, a highly efficient solution is the use of water infrared emitters, which can be radiant panels or radiant profiles that use an intermediate heating medium but do not have many of the limitations inherent in gas systems. A common problem for all types of radiant heating is the lack of a scientifically grounded and generally accepted engineering methodology for its design. Most of the regulatory documents simply do not take into account the peculiarities of the operation of radiant heating systems and, thus, do not allow a number of its advantages to be realized. This research was carried out based on NNGASU Radiant Heating Laboratory, unique in Russia, and is devoted to the peculiarities of the formation of the temperature regime in the premises heated by water infrared emitters, as well as the thermal regime of external enclosing structures in these premises.