Fan Coil Research Articles

Potential of Energy Saving of Propane Heat Pump as replacement of gas boilers with low and high temperature emitters

This work deals with the analysis of the energy performance and the environmental impact of a Heating, Ventilation and Air Conditioning (HVAC) system based on an innovative Air-to-Water electrical Heat Pump (AWHP) using propane (R290) as the refrigerant. A building of the University of Bologna located in Forlì (North of Italy) is considered for replacing a condensing gas boiler and a conventional chiller with an AWHP using R290. To evaluate the efficiency of the existing heating system and the potential savings linked to the adoption of the propane AWHP, the building energy model was created and calibrated by collecting monthly thermal and electrical consumptions as a function of the actual climate data. In this paper, the main features of the R290-based AWHP are described in detail by emphasising the device performance as a function of the operating conditions (i.e., air and water temperature and speed of the scroll compressor). A series of scenarios have been studied to evaluate the energy performance of the propane AWHP with respect to the reference scenario under various operating conditions. The results show that while the total primary energy demand increases adopting the propane AWHP with respect to the case of a gas boiler, the non-renewable primary energy fraction decreases significantly, with a dramatic increase in the renewable quote. From an economic point of view, lower annual costs are obtained by adopting a propane AWHP coupled to fan coils, mainly when the electrical heat pump is used in a thermally insulated building in which a photovoltaic system is installed.

Comparison of Local Mean Age of Air between Displacement Ventilation System and Mixing Ventilation System in Office Heating Conditions during Winter

A novel displacement ventilation system (DVS) was designed using a four-way cassette fan coil unit (FCU) and air purifiers (APs) for supplying clean air. The proposed DVS in this study involved drawing indoor air through the FCU and diffusers installed in the ceiling, controlling air temperature using the FCU, and then discharging it back into the office through the APs placed on the floor. The comparative ventilation system considered was the typical mixing ventilation system (MVS) that intakes and exhausts indoor air using diffusers installed on the ceiling. The local mean age of air was used as an index to compare indoor air quality between DVS and MVS under winter heating conditions. It was found that the DVS was more effective in improving indoor air quality in winter than the MVS. Moreover, compared to the MVS, utilizing the DVS designed in this study resulted in the advantage of a much more uniform air temperature variation in the office space. Therefore, it is anticipated that modifying the structure of an indoor space with an FCU installed in the ceiling and APs on the floor to use the DVS designed in this study would greatly assist in enhancing indoor air quality.

Development of a Building Simulation Model for Indoor Temperature Prediction and HVAC System Anomaly Detection

In order to reduce global energy consumption, energy-efficient, green and smart buildings have to be built. In addition to the application of other energy efficiency measures, an effective management of HVAC systems is required. High quality management and control of these systems ensures optimal occupant comfort levels, proper operation, rational energy consumption, and a positive impact on the environment. This is especially important for large buildings with complex systems such as hotels. As a contribution to the creation of appropriate tools for the management and control of HVAC systems in smart buildings, this paper presents the results of the current development of a detailed dynamic simulation model based on data collected from a smart room system in a hotel in Zagreb, Croatia. The smart room system, which is integrated into the hotel's building management system, provides historical data on set and current room temperatures, room occupancy schedule, window opening, fan coil operation status, fan rotation speed, valve opening, and operating mode with a time step of 5 minutes. The simulation model based on the TRNSYS software uses a part of the available data and calculates the current internal room temperatures. A comparison of the predicted and measured temperatures at each time step showed that the deviations are within the acceptable limits. The final objectives of the model development are the identification of anomalies in the operation of the HVAC system and the optimization of its operation with the aim of reducing energy consumption.

Parametric analysis of chiller plant energy consumption in a tropical climate

The approach that could reduce the energy consumption of water-cooled chillers in office buildings was investigated through experimental and simulation methods. The chiller was modelled in TRNSYS and validated using physical measurements from an operational water-cooled water chiller and fan coil system. The validated model was used to analyse the energy consumption of the water chiller-fan coil system under a high chilled water temperature setpoint (CWTS) in a representative commercial office building. Subsequently, indoor thermal comfort was evaluated using the PMV-PPD model. Finally, the design of experiment (DOE) was employed using a statistical two-level non-randomized factorial design in Minitab to study the effects of high CWTS, number of rows, and tube diameter on the heat and mass transfer performance of the fan coil unit. The results showed that the CWTS can be increased by various degrees from 10 up to 18 °C for energy efficiency for a commercial office building in the tropics. This increase in CWTS would result in a daily energy saving potential of about 5% of the chiller as compared to the existing operational settings without any extra cost. Conversely, the daily energy consumption by the fan coil would increase by about 5.5% by this increment in the CWTS. It was determined that the chiller system can provide comfort even when the CWTS is increased to 14 °C. The DOE analysis showed that under the condition of high CWTS (14 °C), energy consumption that is less than the current energy consumption may be expected from the fan coil system when the number of rows increased from 3 to 6 and the tube diameter increased from 7 to 9 mm.

Priori knowledge-based deep reinforcement learning control for fan coil unit system

Controlling the water pump and fan in the heating, ventilation and air-conditioning (HVAC) system is crucial for achieving optimal performance of the fan coil unit (FCU) systems. In this paper, the researchers investigate the control problem of the FCU system under the model-free assumption. Specifically, the researchers innovatively model the control problem of the FCU system as a Markov decision process (MDP) and optimize the FCU control using reinforcement learning (RL) methods. However, exploration strategies in the early stage of control using RL methods can lead to poor control performance. To address this, a novel deep deterministic policy gradient control method based on the priori knowledge (DDPG-PK) for the FCU system is proposed, which combines priori knowledge and deep reinforcement learning (DRL) algorithms, following human experience to avoid bad control behavior and achieve better policy control. To validate the performance of the proposed algorithm, the researchers build a variable operating conditions simulation model based on the actual parameters of the real FCU system and related historical data on a general thermodynamic basis. Experimental results show that, compared to other benchmark methods, the DDPG-PK method improves the FCU system's 27.5% satisfaction rate and 23.0% energy efficiency rate in the first three years, and can still keep a state-of-the-art performance in following years.

RETRACTED: An innovative simulation-based methodology for evaluating cooling strategies in climate change-induced overheating

As global climate change progresses the built environment grapples with the increasing challenge of overheating. In response to these challenges, this study introduces an innovative simulation-based methodology aimed at enhancing the resilience and sustainability of cooling strategies. The proposed methodology utilizes weather and building data characterization, user clothing behavior, and cooling strategy selection. The methodology relies on three main indicators: Indoor Overheating Degree (IOD), Ambient Warmness Degree (AWD), and Climate Change Overheating Resistivity (CCOR). It also considers sub-indexes like analysis of greenhouse gas emissions, energy consumption, Exceedance Hours, and the average Predicted Percentage of Dissatisfaction. This comprehensive approach allows for a multi-zonal assessment of indoor overheating risk and resilience to climate change, to validate the methodology ‘s effectiveness, we conducted a thorough comparison, focusing on Packaged Terminal Heat Pumps (PTHP) (C01) and Fan Coil Units (FCU) (C02) in six selected reference cities with different climates. The case study employs a shoebox model to depict a double-zone office and administration building. In general, C01 demonstrates greater resistance to climate change-induced overheating compared to C02. The highest CCOR value, 58.16, is found in C01 in Vienna, while the lowest CCOR value, 12.7, is observed in C02 in Montreal, indicating the lowest resistance. Furthermore, this study underscores the pivotal importance of meticulously evaluating the susceptibility of cold cities to the imminent impacts of climate change and the urgency of implementing proactive strategies to bolster their resilience.

Empirical investigation of occupant-centric thermal comfort in hotel guestrooms

Given the importance of occupant satisfaction with thermal comfort in hotel accommodations, previous studies have assessed thermal comfort using either local or global standards. In a hotel catering to diverse guests, a single standard may constrain the formulation of an optimal strategy for improving occupant satisfaction. To address this challenge, this study empirically investigates occupant-centric thermal comfort in hotel guestrooms located in a hot and humid climatic region. To this end, a living-lab-based case study was conducted on a hotel guestroom in Hong Kong, wherein two types of thermal comfort improvement strategies were devised from both local and global perspectives. First, to improve thermal comfort in line with the local standard, it was determined that an ancillary fan coil unit (FCU) energy consumption of 6.0 kW h (approximately 34 % of the existing energy consumption) was required. Second, to improve thermal comfort in line with the global standard, an ancillary FCU energy consumption of 9.4 kW h (approximately 53 % of the existing energy consumption) was necessary. Consequently, in a hot and humid climatic region, the distribution of thermal comfort may vary depending on the type of guest (e.g., domestic or foreign), and ancillary cooling energy expenditure may be incurred to enhance a guest's thermal comfort. The proposed approach is expected to contribute to the creation of occupant-tailored thermal comfort by considering an individual's thermal acclimation to a specific climatic region from both local and global perspectives.

Experimental study to understand the thermal environment of an office cooled by radiant ceiling panels and dedicated outdoor air system

This research aims to better understand the radiant environment of an interior space located in the tropical climate that is cooled by Radiant Ceiling Panels (RCPs). To do so, we have designed a highly instrumented 177m2 office testbed in Singapore installed with RCPs, Dedicated Outdoor Air System (DOAS) and Fan Coil Units (FCUs). An 11-day experiment is designed to monitor the radiant environment when being cooled by 1) RCPs + DOAS and 2) FCUs + DOAS with a fixed internal load of 2kW and humidity load of 8g/hr. We alternate between these two cooling modes, with variations in panels’ water supply temperature and window blinds. We expect to see a separation of Mean Radiant Temperature (MRT) and air temperature in mode 1 with the use of improved radiant sensors. However, results showed only minor differences in the radiant environment between the two modes of cooling. There was no significant MRT and air temperature separation (<1°C). These insights provide a better understanding of our radiant environment, which can potentially improve the way we control radiant systems. With better understanding, we can support high thermal comfort performance of a radiant systems as compared to a more common air-based system.

Comparative analysis of heating characteristics of convective-radiant systems using various terminal air source heat pumps

The escalating demand for efficient heating solutions in hot summer and cold winter area has directed substantial attention towards convective-radiant combined systems. These systems offer enhanced comfort while conserving energy. In the context of office buildings, it becomes imperative to consider structural attributes. Under identical operational strategies, disparities in energy consumption and thermal comfort arise from variations in water supply temperature and terminal configurations. Here, we have established a dedicated laboratory to examine convective-radiant heating systems utilizing air source heat pumps. The primary objective is to analyze the impact of distinct heating terminal types and water supply temperatures on indoor thermal comfort, energy consumption, and energy efficiency. By analyzing the dynamics of indoor parameter, and interrelations among air temperature, average radiant temperature, operative temperature, and comfort levels, optimal strategies are determined. Empirical findings demonstrate that independently opening the Fan coil convection system (FC) leads to significant fluctuations in air temperature and creates an unstable heat environment. However, the Radiant floor system (RF) and Convective-radiant combined heating systems (FC + RF) exhibit superior stability in maintaining indoor air temperature. Compared among the three systems, while FC displays the lowest energy consumption upon activation, it compromises comfort levels. Remarkably, there is a strong relationship between operative temperature and Predicted Mean Vote (PMV) for the three systems, with high correlation coefficients of 0.998, 0.999, and 0.997, respectively. Conversely, the association between air temperature and PMV proves weak, with correlation coefficients of only 0.415, 0.469, and 0.841. Consequently, it is advised to prioritize operative temperature as the benchmark for winter air temperature control. For sustained adherence to Level II comfort zone criteria during indoor occupancy, it is recommended to employ (FC + RF) or RF for winter heating. Notably, energy savings of 26.87 %, 30.07 %, and 32.86 % are respectively achieved for (FC + RF), FC, and RF configurations when utilizing a water supply temperature of 35℃ as opposed to 45℃. Hence, the adoption of low-temperature water heating during winter is strongly advocated.

Is a fan coil unit (FCU) an efficient cooling system for net-zero energy buildings (NZEBs) in tropical regions? An experimental study on thermal comfort and energy performance of an FCU

In tropical regions, the selection of an efficient cooling system is a prerequisite for energy-efficient and net-zero energy buildings (NZEBs), while fan coil unit (FCU) systems are commonly used to provide thermal comfort (TC) of the interior environment throughout the entire year. In this study, to find a cooling solution for Malaysia's first net-zero building, the performance of a case study FCU-classroom was evaluated based on a one-month experimental assessment and a one-year simulation function. The precision of the measurements was computed using uncertainty analysis, and the simulation model was validated using measurement data. The impact of mechanical dehumidification on FCU performance was evaluated by analyzing the collected data in terms of cooling load allocation, cooling coil capacity, TC, and energy consumption. In order to guide the selection of a cooling system, a comparative analysis has been conducted between the performance of the FCU and two alternative systems, namely the redesigned FCU and the desiccant cooling system. This analysis was focused on evaluating the TC and energy use of these systems. The findings from the FCU performance analysis indicated that, in order to handle the cooling load in a classroom with an equal distribution of latent and sensible load (50:50 ratio), the FCU utilized 56 % of its total cooling coil capacity (13.06 kW) and 37 % of its energy consumption for the dehumidification process. The FCU utilized an average of 1360.3 kWh per month to maintain a comfortable room temperature of 24.3 °C and an uncomfortable relative humidity (RH) of 77.2 %. However, it was observed that the amount of moisture removal was insufficient to achieve a humidity comfort level in the room. Comparing alternative solutions to the FCU revealed that while a redesigned could provide TC, it consumed approximately 1.6 times more energy per month than the FCU. The desiccant cooling system provided TC with an average monthly energy savings of 37.8 % compared to the case study FCU.

Control-oriented fan coil unit modeling for room dynamics considering dehumidifying cooling conditions and indoor air quality

This paper studies a control-oriented fan coil unit (FCU) modeling problem, which takes into account latent heat for the process of dehumidification during cooling analyses and indoor air quality. A single-zone room model is studied by considering the thermal, humidity, and CO2 dynamics, and an FCU model is built by simulating both sensible and latent heat exchange considering three different types of conditions (completely dry, completely wet, and partially-wet-partially-dry). The process of dehumidification in the FCU is very complex and challenging to model and is affected by multiple coupling factors such as the structure of the FCU, the temperature and flow rate of air and refrigerant, etc. The proposed FCU model includes the process of heat exchange under the aforementioned conditions of the FCU so that the dynamics of room temperature and humidity can be obtained. The speed of the fan and the position of the damper inside the FCU are controlled for the integration of the room and FCU models. The simulation results show that the proposed control methods are effective in maintaining the temperature, humidity, and CO2 concentration level in the desired ranges for cooling conditions with dehumidification.

Neural network approach for quick dimensioning of energy walls

neural network approach for quick dimensioning of energy walls

Research on energy consumption analysis of air conditioning and refrigeration equipment based on perceptron model

Abstract This paper mainly studies the energy consumption of air conditioning and refrigeration system from the perspective of the dynamic operation of air conditioning systems and selects the energy consumption of a chiller system, cooling tower system, chilled water pump system and fan coil system, which affect the energy consumption of air conditioning system, as model variables. An integrated learning method based on a multilayer perceptron is proposed to integrate spatial features with temporal features, and a spatio-temporal prediction model for air conditioning energy consumption analysis is established under the Seq2Seq framework, and then the input curves of the four variables with load change under the optimal operation of the air conditioning system under dynamic load are derived. The results show that the deviation between the simulated value and the measured, calculated value of the energy consumption analysis model of air conditioning and refrigeration equipment based on the multilayer perceptron is within 5%, which can effectively and accurately predict and reduce air conditioning energy consumption by 15% to 20%. The maximum energy-saving efficiency can reach 30% when the air conditioning system is in optimal operation under dynamic load, and the energy-saving effect of the chiller, chilled water pump and cooling water pump is relatively significant. The research results of this paper have a certain reference value for reducing the energy consumption of air conditioning systems in practice.

Performance analysis of a multi-source renewable energy system for temperature control in buildings of varied thermal transmittance and climate zone

The current paper presents a numerical analysis of a multi-source renewable energy system for building air conditioning aiming at decarbonising the building envelope. The thermal management of the building is pursued through a radiant floor fed by a heat pump and integrated with phase change materials for thermal inertia enhancement. A fan coil is foreseen for humidity control. The heat pump can be fed through three parallel circuits involving different thermal sources: air with an ordinary air-to-water heat exchanger, sun through photovoltaic thermal solar collectors, and ground using shallow ground flat-panel heat exchangers. At need, the ground can be exploited for thermal energy storage when the heat pump is idle. A set of dedicated control rules chooses the optimal source or mix of sources to exploit at any time. Simulations of a reference building, namely a large single-room snack bar, are performed for various plant configurations, hypothesising the building as located in distinct climate zones and characterised by different thermal transmittance. The thermal performance of the building is given in terms of primary energy needs per year and compared to that of an analogous single-source plant. Results show that the proposed system can lead to primary energy savings of up to 16% compared to the corresponding state-of-the-art single-source plant, being more effective if the geothermal field is large enough and the building heating and cooling needs are comparable. The relevance of a proper control algorithm for plant performance optimisation is highlighted: a thermal power-based approach is proposed and successfully tested.

A comparative thermoeconomic analysis of fourth generation and fifth generation district heating and cooling networks

The energy refurbishment of residential heating and cooling systems is crucial to achieve the carbon neutrality expected by 2050. In this framework, many researchers are developing low-temperature district heating and cooling systems, integrated with renewable technologies. In particular, fourth-generation district heating and cooling systems are largely used, and a considerable number of these systems have been installed in the last few years. This is due to the wide use of heat pumps and low-temperature heating terminals, such as radiant floors and fan coils. Fifth generation district heating and cooling systems include several significant advancements with respect to the previous technology. This research proposes a thermoeconomic comparison between fourth generation and fifth generation district heating cooling networks, including ground-source heat pumps, supplying heating and cooling energy to a residential district located in Leganes, Madrid. The thermal load of the residential district network is simulated by means of detailed models of the buildings. In the proposed systems, the electric load is partially met by a 3 MW photovoltaic field. The dynamic simulation model of such districts is developed in TRNSYS18, including detailed models for each component. Both the analysed technologies achieve very promising results from both economic and energy points of view. The Primary Energy Saving for the 4th and 5th generation districts are equal to 97% and 81%, respectively. Finally, 4th and 5th generation networks determine a reduction of the CO2 emissions by the 98% and the 87%, respectively. The development of innovative district heating and cooling systems is crucial for the reduction of the environmental impact of buildings sector. However, for residential applications, novel 5th generation networks do not exhibit a better energy and economic performance with respect to mature 4th generation networks, due to the scarce simultaneous heating and cooling demand.

Improving the Efficiency of Fan Coil Units in Hotel Buildings through Deep-Learning-Based Fault Detection.

Optimizing the performance of heating, ventilation, and air-conditioning (HVAC) systems is critical in today's energy-conscious world. Fan coil units (FCUs) play a critical role in providing comfort in various environments as an important component of HVAC systems. However, FCUs often experience failures that affect their efficiency and increase their energy consumption. In this context, deep learning (DL)-based fault detection offers a promising solution. By detecting faults early and preventing system failures, the efficiency of FCUs can be improved. This paper explores DL models as fault detectors for FCUs to enable smarter and more energy-efficient hotel buildings. We tested three contemporary DL modeling approaches: convolutional neural network (CNN), long short-term memory network (LSTM), and a combination of CNN and gated recurrent unit (GRU). The random forest model (RF) was additionally developed as a baseline benchmark. The fault detectors were tested on a real-world dataset obtained from the sensory measurement system installed in a hotel and additionally supplemented with simulated data via a physical model developed in TRNSYS. Three representative FCU faults, namely, a stuck valve, a reduction in airflow, and an FCU outage, were simulated with a much larger dataset than is typically utilized in similar studies. The results showed that the hybrid model, integrating CNN and GRU, performed best for all three observed faults. DL-based fault detectors outperformed the baseline RF model, confirming these solutions as viable components for energy-efficient hotels.

BIM-Based Automated Multi-Air Distribution Layout Generation for Office Buildings: A Case Study

Although HVAC (Heating Ventilation, and Air Conditioning) layout design has transitioned from 2D drawings to 3D BIM models, the traditional manual process of sizing and placing terminal units is still a time-consuming task, which can lead to inappropriate airflow and wastage of resources due to human error. The purpose of this paper is to develop a highly robust method for sizing and placing HVAC terminal units in rooms, while also systematically avoiding obstacles based on the locations of air terminal units and FCUs (Fan Coil Units) to which they belong. The method employs a “scan” approach to solve the problem of insufficient robustness caused by the traditional grid division method. Rule-based iterative algorithms are utilized for the sizing of terminals, airflow verification, and obstacle avoidance to generate a complete set of FCU and CAV (Constant Air Volume) system terminal layouts within a building. The method was tested for the automated design of HVAC terminal layouts in six different buildings and successfully completed the task within seconds, demonstrating the method’s immediacy and robustness. Moreover, airflow organization tests showed that the terminal layouts generated by the algorithm had a 95% pass rate, indicating the effectiveness of the method.

Experimental study on the operating characteristic of a combined radiant floor and fan coil heating system: A case study in a cold climate zone

Experimental study on the operating characteristic of a combined radiant floor and fan coil heating system: A case study in a cold climate zone

수열 이용 히트펌프 시스템의 열원 측 배관 설계 변수에 따른 동력소비량 변화 분석

The power consumption of pumps in a hydrothermal heat pump system is important from environmental and economic points of view. In this study, an office building and a hydrothermal heat pump system were modeled by the TRNSYS 18 program, and building load and energy consumption were simulated. The variation in pump power consumption was analyzed according to changes in the design parameters for heat source-side piping in the heat pump system. The system consisted of a heat pump, pumps, heat exchangers, and a fan coil unit. The flow rate and power consumption of the pumps and the fan were calculated by the system operating time to satisfy the building load. A simulation was performed by changing the horizontal distance to the hydrothermal source from 200 m to 1000m, vertical height differences from 2 m to 10 m, and pipe diameters from 0.1 m to 0.3 m. The intake pump (Pump A) power consumption ratio to total power consumption increased from 6.5% to 11.7% with increases in the distance to the hydrothermal source. The simulation results showed that the pipe diameter had a great influence on the power consumption of the pump.

Amount of heat available from a prosumer of a 5th generation district heating and cooling (5GDHC) system: Case study of a data center

The research problem is no method to estimate the specifications of a data center when no design data is available. The aim is to check capacities and temperature levels to supply energy to a 5th generation district heating and cooling (5GDHC) system. The methodology includes studying satellite images and design documents of similar projects. Ventilation chambers, roof-top units (RTUs), dry coolers, and free cooling chillers are recognized on satellite images. We study the layout of the heating, ventilation, and air-conditioning (HVAC) system, technological limitations, and server and cooling loads. The results suggest excluding RTUs, adding adjusting factors to dry coolers, and investment costs for the conversion from air to water cooling. Chillers and fan coil units operate in partial load mode to ensure the reliability level. Waste heat varies, although server power consumption remains constant. The configuration to utilize the waste heat is suggested. It includes a separate free-cooling heat exchanger, which allows turning off the compressors when the outdoor temperature drops. Variable supply and return temperatures compensate for the variation in outdoor temperature. In summer, the return temperature is high enough to supply heat directly to the 5GDHC network. In winter, heat pump boosting is necessary; the preferable outdoor temperatures are 0–10 °C. The implication is that water cooling increases data center feasibility as a prosumer for 5GDHC. The novelty is a method to assess how much energy is possible to recuperate; specific energy consumption/production is justified. The value is the solution to further decarbonize the energy industry and increase energy efficiency is suggested.