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Mechanical Ventilation with Heat Recovery (MVHR) systems are gaining increasing interest in buildings with low energy demand, for improvement of the Indoor Air Quality (IAQ) and reduction of the ventilation energy loss. In retrofitted buildings, MVHRs are often integrated with an additional air heater to cover space heating demand. Hence, evaluation of the interactions between MVHR and heat emitter, and their effects on indoor airflow characteristics is of significant importance. The present study aims to investigate effects of a combined MVHR-fan-coil system in heating mode on IAQ and thermal comfort parameters inside a retrofitted room, by means of a computational fluid dynamic (CFD) code. The proposed CFD model is validated by comparing the numerical results with experimental data. The results yielded by numerical simulations allow evaluating the indoor environmental quality characteristics as well as addressing the MVHR and fan coil interactions. The results indicate that the airflow discharged from the fan coil could have a significant impact on the age of the air; while it provides a desirable thermal comfort condition within the room, it may hinder to some extent delivery of the fresh air to the occupied zone due to creation of counterflow fields. Furthermore, it is shown that although increasing the fan speed (ON mode) would slightly enhance the air change efficiency, the OFF mode yields not only a better distribution of the fresh air but also a higher ventilation efficiency than when fan coil operates.

Air source heat pumps (ASHPs) are widely used in various types of buildings in different regions of China. Considering the significant differences in the characteristics in heat source side and user side, providing different products for different zones is an effective strategy to promote the systematic development of the ASHP technology. To realize the goal of energy conservation, standard rating conditions are extremely important. The principles for determining the standard rating conditions based on a two-side (heat source/user side) multi-grade (different conditions) method were proposed along with the development of related standards. Therefore, the establishment of standard rating condition is introduced and summarized systematically. For heat source side, the standard rating conditions for heating were classified into four types according to the lowest ambient temperature (−25, −12, −2, 7 °C), while for cooling they were constant (35 °C). For user side, the conditions for supply air (20/27 °C for heating/ cooling), floor heating (35 °C), radiator (50 °C), fan coil unit (41/7 °C for heating/cooling), domestic hot water (55 °C), and industrial use were also determined. This study introduced the implications on ASHP by different standard rating conditions, especially the technical requirements, which indicated the necessity of providing different system cycles and compressors. The energy savings and economic benefits were also evaluated. The primary energy saving rate reached 15.3% and 41.6% compared with coal heating and conventional ASHP respectively by using low ambient temperature ASHP. The results showed that these standards have been satisfactorily developed.

Объём потребления энергии, в том числе и электрической, в нашей стране непрерывно увеличивается. В связи с этим возникает необходимость максимального снижения затрат электрической энергии. В статье рассматривается возможность снижения электрической энергии в приточных системах вентиляции за счёт использования вентиляторов-доводчиков. Приведены результаты аэродинамического расчета двух вариантов приточной системы вентиляции промышленного здания. Первый вариант - традиционная схема с одним общим центральным вентилятором. Второй вариант - схема с использованием вентиляторов-доводчиков на отдельных ветвях системы. В результате проведенных расчетов показано, что установка вентиляторов-доводчиков позволит существенно снизить нагрузку на привод центрального вентилятора. The volume of energy consumption, including electricity, in our country is constantly increasing. In this regard, it becomes necessary to reduce the cost of electrical energy as much as possible. The article discusses the possibility of reducing electrical energy in supply ventilation systems through the use of fans. We present the results of the aerodynamic calculation of two variants of the supply ventilation system of an industrial building. The first option is the traditional scheme with one common central fan. The second option is a scheme using fan coil units on separate branches of the system. As a result of the calculations, it is shown that the installation of fan coil units will significantly reduce the load on the central fan drive.

Temperature and humidity independent control (THIC) air-conditioning system is a promising technology. In this work, a novel temperature and humidity independent control (THIC) system is proposed, namely VMD-ACERS, which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system. This work establishes a novel coefficient of performance (COP) model of VMD-ACERS. The main parameters affecting the COP of conventional fan coil unit cooling system (FCUCS) and VMD-ACERS are investigated. The performance of FCUCS and VMD-ACERS are compared, and the energy-saving potential of VMD-ACERS is proved. Results indicate that, for FCUCS, the importance ranking of parameters is basically stable. However, for VMD-ACERS, the importance ranking will be affected by FCU and refrigerant. The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure. On the contrary, superheating, subcooling are relatively less important parameters. For VMD-ACERS, it is not necessary to pursue the membrane with very high selectivity, because the selectivity of membrane would also be a less important parameter when it reaches 500. The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 kPa. The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC, and can extend the application of THIC air-conditioning system.

For thermal comfort and energy-saving performance, a floor-heating method is superior to conventional heating modes, e.g., radiator, fan coil, etc. The floor-heating method has been developed to be a primary indoor heating form. Wood is the most common floor surface material. Due to the anisotropy of wood, it is difficult to obtain a general theoretical formula for its thermal physical properties. In this paper, intelligent algorithms were adopted to predict thermal conductivities of wood. First, the study elaborated frequently used testing methods of thermal conductivity. Next, 130 types of common wood species were measured to form a database of thermal properties. With this database, intelligent algorithms were used to make predictions. For the thermal conductivity predictions that were conducted with support vector machine, the degree of fit between the predicted results and the measured results was not less than 0.87 (k-fold validation). This study validated the feasibility of the usage of the intelligent algorithm for the research and prediction of the thermal conductivities of wood.

The traditional integer order PID controller manipulates the air-conditioning fan coil unit (FCU) that offers cooling and heating loads to each air-conditioning room in summer and winter, respectively. In order to maintain a steady indoor temperature in summer and winter, the control quality cannot meet the related requirements of air-conditioning automation, such as large overshoot, large steady state error, long regulating time, etc. In view of these factors, this paper develops a fractional order PID controller to deal with such problem associated with FCU. Then, by varying mutation factor and crossover rate of basic differential evolution algorithm adaptively, a modified differential evolution algorithm (MDEA) is designed to tune the satisfactory values of five parameters of indoor temperature fractional order PID controller. This fractional order PID control system is configured and the corresponding numerical simulation is conducted by means of MATLAB software. The results indicate that the proposed fractional order PID control system and MDEA are reliable and the related control performance indexes meet with the related requirements of comfortable air-conditioning design and control criteria.

Current study is aimed at making the most appropriate design considering the dynamic energy, exergy and economic analysis of Ground Source Heat Pumps (GSHP). The energy required to heat and to cool a 200 m2 office in Istanbul is determined, and based on these data, the entering and leaving water and soil temperatures of horizontal Ground Heat Exchanger (GHE) are obtained numerically for a ten-year period with realistic boundary conditions using meteorological data. The results obtained from the numerical study are confirmed by GHE experimental setup built in Yildiz Technical University. The variations of COP, second-law efficiency and exergy destruction of each component of GSHP at both seasons of the first, fifth and tenth years are obtained for Radiant Wall Panel Unit (RW-PU), Floor Heating + Fan-Coil Unit (FH-FCU) and Radiator + Fan-Coil Unit (R-FCU) systems. At the end of the 10-year dynamic simulation period of the GSHP system, the average values of COP and second law efficiency for RW-PU, FH-FCU and R-FCU are found as 4.01, 3.37, 3.01, and 39.29%, 38.04%, 36.63%, respectively. Furthermore, considering the initial investment and operational costs of RW-PU, FH-FCU and R-FCU systems integrated into the GSHP system, an objective function is defined as an optimization parameter.

The goal of this paper is to quantify the impact of weather-induced and altitude-induced barometric pressure variations on the cooling capacity measurement of hydronic coils in room fan coil units....

In consideration of the lowered heating and cooling load of ultra-low energy buildings, a natural heat transfer air-conditioning terminal device (NHTACTD) is presented by the authors. The terminal device is able to undertake heating, cooling and moisture load of a room according to the inlet water temperature. Its comparative advantages are pointed out by comparing it with radiators, fan coil units, chilled beams and radiant heating and cooling terminals. After the actual thermal properties of the NHTACTD are provided, three air-conditioning system configuration schemes based on the NHTACTDs are presented: (1) In the NHTACTDs plus fresh air system, the NHTACTDs and the fresh air handling unit undertake all the air-conditioning load of the system together, and it is used where high indoor air quality is demanded; (2) In the scheme of the air-conditioning system including the NHTACTDs only, all the air-conditioning load of the system has to be undertaken by the terminals alone and it is used where high indoor air quality is not rigidly demanded. (3) In the scheme of the air-conditioning system including both the NHTACTDs and radiant panels, the NHTACTDs undertake all the moisture load of the system, and the remaining sensible cooling load is undertaken by the radiant panels. The scheme can be used where there is large sensible cooling load while high indoor air quality is not rigidly demanded. Then an ultra-low energy residential building is taken as a case project to elaborate the design method of an air-conditioning configuration scheme based on the terminal device with the help of psychrometric chart.

When the performance test is carried out for a water-cooled chiller, a thermostatic water tank, as an indispensable part of the testing apparatus, takes the main responsibility for the waterside working condition. In this paper, a single energy-saving thermostatic water tank is proposed to treat chilled water and cooling water drained out of water-cooled chiller and supply chilled water and cooling water at the required temperature with stable performance. The water tank works with inside and outside water flow circuit simultaneously. The inside water flow circuit takes place within three districts in the water tank divided by two baffle configurations. The outside circuit includes the water tank, a cabinet fan coil and an air-cooled chiller. Experiments are operated to obtain and analyze temperature distribution in water tank with 5 arrangements of baffle configurations to find the optimal model. Using this optimal water tank model, notched baffles are altered into baffles at 6 perforation rates from 15% to 100% respectively for further experimental analysis. Thereby the most favorable perforation rate is found. Experimental results show that the further optimized water tank provides water at design temperature stably using baffle configurations arranged in model 5 with perforation rate from 25% to 50% under 4 representative working conditions. Performance of the water tank is evaluated by the spatial temperature uniformity coefficient proposed in the paper. Evaluation results verify the reliability of the optimal water tank and determine the perforation rate to the range from 25% to 60%.

Air conditioning engineers design the inlet or outlet position of a fan coil unit (FCU) system according to thermal comfort and cost. However, the effect of the position on fire growth has not been...

(1) Background: Many schools and higher education settings have confronted the issue of reopening their facilities after the COVID-19 pandemic. In response, several airflow strategies spanning from adding portable air purifiers to major mechanical overhauls have been suggested to equip classrooms with what is necessary to provide a safe and reliable environment. Yet, there are many unknowns about specific contributions of the building system and its design and performance on indoor air quality (IAQ) improvements. (2) Methods: this study examined the combined effect of ventilation type, airflow rates, and filtration on IAQ in five different classrooms. Experiments were conducted by releasing inert surrogate particles into the classrooms and measuring the concentrations in various locations of the room. (3) Results: we showed that while the distribution of particles in the space is a complex function of space geometry and air distribution configurations, the average decay rate of contaminants is proportional to the number of air changes per hour in the room. (4) Conclusions: rooms with a central HVAC system responded quicker to an internal source of contamination than rooms with only fan coil units. Furthermore, increasing the ventilation rate without improved filtration is an inefficient use of energy.

The thermal comfort level of Chinese residents in the hot-summer and cold-winter zone is increasing with economic development in recent years. More district heating and cooling systems were installed in these areas. Supported by the government, ground source heat pump (GSHP) is used as a common environmentally friendly district heating and cooling system in many residential communities. However, the evaluation of the real performance of GSHP is limited, especially limited understanding of the common issue of thermal imbalance of GSHP systems over several years—the mismatch between heat extraction from and rejection to the ground. Performance of GSHP systems can deteriorate over years if the thermal imbalance is significant and not addressed. For GSHP in the hot-summer and cold-winter climate zone, there are few thermal imbalance studies based on real field data and modeling. To address this gap, this paper proposes an integrated simulation model to evaluate thermal imbalance of GSHP systems considering key influencing factors including occupant behavior and heat pump performance. A case study was conducted to simulate and analyze the actual operation of GSHP in Chinese residential buildings. The indoor comfort temperature setting and flexibility of residents’ control on indoor terminal air-conditioning units determine the actual heating and cooling demand in residential buildings, which resulted in differences in thermal imbalance for GSHP systems. It was found that GSHP systems with radiant floor only for heating lead to the most severe thermal imbalance, while GSHP systems with fan coil units or radiant ceiling for cooling and/or heating achieved much better thermal balance. The proposed thermal imbalance ratio is an important indicator that can be used to evaluate thermal imbalance of GSHP systems and thus inform their design and operation for energy efficiency.

This study assessed through numerical simulations, the technical feasibility of a solar-powered absorption cooling system for a small-scale application in an office building in three different cities with a tropical climate in Ecuador. The model and simulations were performed using the dynamic transient software TRNSYS and were compared and validated using experimental data obtained from a real-life system with main components: 12 m2 vacuum tube solar thermal collector array, a 4.5 kW LiBr/H2O single-effect absorption chiller, a 6 kW fan coil and a 100 l sensible cold store. The results of the simulation showed a good agreement with the experimental data with a deviation of 8.5%. The validated model was used to undertake a parametric study to determine capacities of systems that will be applicable to three Ecuadorian cities: Guayaquil, Manta and San Cristobal. The system capacity predicted by the model for the Ecuadorian cities has the following components: 24 m2 evacuated tube collector field, a 20 kW heat exchanger, a 15 kW single-stage LiBr/H2O absorption chiller, a 35 kW cooling tower and a cold storage tank of 2 m3. The results showed that the proposed system could meet most of the required cooling load (90% for Guayaquil and San Cristobal, and 71% for Manta, considering a set point of 24°C) of a typical single-story office building with.

In this study, increasing efficiency of a heat exchanger as a sub part of concealed ceiling type fan coil unit is aimed. Accordingly, by determining rotational speed of fans based on actual design; generated air distribution in dry condition on heat exchanger is investigated via computational fluid dynamics software. Significant low air distribution is detected in lower and higher sides of the heat exchanger. In order to create solution to this issue and to increase efficiency, by designed air distributor, homogenized air distribution is targeted. As a conclusion, differentiation of air velocities and air distribution is investigated based on various angles. By means of the distributor with an optimum design angle, air distribution is improved and more homogenous air distribution is achieved.

The design and construction of a cold production system from the ice water submitted by a mechanical direct expansion system contributing to the development of knowledge in the area of air conditioning were carried out. Among the technical design parameters, a direct expansion system with cooling capacity of 9000 BTU/Hrs, R134 refrigerant gas to a turbine for the work of the Fan Coil of ½ Hp of force 220 V was selected, as was the fan motor of the cooling tower as fundamental means for heat transfer. The recirculation pumping system is carried out by pumps of 0.37 kW of power and a maximum flow of 40 l/min. For both the evaporator sump (cold) and the condenser sump (hot). The work stage is given in two independent circuits, the Fan Coil system is connected to the evaporator sump and the cooling tower, in turn, is connected to the condensation system for proper operation and achieve condensation temperatures of 35 ° C and in case of having water requirements in the cold sump, the tower is connected by means of an electromagnetic valve for its supply.

The purpose of this study was to provide in situ field data on fan/motor efficiency and fan static pressure differentials for the fan/motor combinations used in fan coil units. Measurements were ma...

Eksperimental studi pada Fan Coil Unit (FCU) dilakukan untuk menginvestigasi karakteristik perpindahan panas akibat penambahan nanopartikel Al2O3. Tujuan penelitian ini adalah untuk mengungkap fenomena pengaruh nanofluid partikel pada indikator kinerja perpindahan panas. Pada penelitian ini digunakan FCU jenis tube and fin dengan fluida dingin adalah nanofluid Al2O3 dan fluida panas adalah udara. Laju aliran volume fluida dingin 15 lpm dan laju aliran massa fluida panas sebesar 0,48 kg/s. Konsentrasi nanopartikel yang digunakan pada penelitian ini adalah 0,1%. Temperatur udara lingkungan masuk FCU adalah 28±0,50C sedangkan temperatur fluida dingin yang memasuki FCU adalah 19±0,50C. Pada penelitian ini parameter kinerja pada fluida dingin dengan nanopartikel dibandingkan dengan tanpa nanopartikel. Hasil penelitian menunjukan pemakaian nanopartikel pada fluida dingin mampu meningkatkan perpindahan panas pada FCU sebesar 9,2%.

The high share of buildings in energy consumption and carbon dioxide emission has led researchers to seek techniques to reduce energy consumption in this sector. In this study, considering a hot and arid climate region, the wall’s heat gain was investigated. To reduce energy demand, three techniques of adding PCM, combining absorption chiller with a solar system and dispersing nanoparticles were used and the results were evaluated transiently. In July, the addition of PCM to the building's walls reduced the heat exchange between interior and exterior spaces up to 21%. To cool the interior spaces, the combination of absorption chiller + fan coil was used and several flat plate collectors were integrated with it to reduce energy demand. By collecting energy in solar collectors and using a stratified tank, energy consumption in the generator section was reduced by 450 kWh. Nanoparticles were used to improve the solar system performance and it was found that loading ZnO and Al2O3 nanoparticles is useful. Dispersing ZnO into water increased the energy-saving by 9.5% while the second nanoparticle improved it by 14.5%.

Air conditioning systems have become essential equipment in many buildings. However, fire safety design and management in buildings rarely consider whether to turn the system off or keep it on in a fire. This study ignites a stack of wood in a room center or corner to explore the influence of air inlet actions of a fan coil unit (FCU) with the door opened or closed. Simulation results using Fire Dynamics Simulator (FDS) demonstrate that the heat release rate (HRR) and room temperature obviously decrease when the room doorway is closed, regardless of whether the air conditioner is turned on. The air supply for combustion is poor. When the door of the room is opened, turning off the air conditioner can effectively reduce the HRR and the room temperature in the early stages of fire growth. However, along with the fire growth, turning on air conditioning can help decrease the heat radiation feedback and the consequent HRR. Therefore, the conclusion that air conditioning always enhances a fire because it provides oxygen may not always be correct.

Buildings are one of the largest consumers of energy in the world and as such an opportunity for significant energy savings. Modelling of user behavior is a prerequisite for predicting the building energy consumption that offers a possibility to adapt the building operation to best suit the user requirements while achieving minimal energy consumption through room air conditioning. In this paper, a deep learning model for prediction of an individual room temperature setpoint provided by the user is presented. Model learning was conducted on the available dataset containing external weather and internal climate measurements. External weather conditions consist of air temperature, relative humidity and direct, diffuse and global solar irradiation. The internal conditions refer to four offices for which the air temperature, the mode of operation of the fan coil controller and the temperature setpoint are available. The model was built using a neural network with Long Short- Term Memory. The highest accuracy was achieved by the model in which the variables on the old setpoint, system working, day of the week and relative humidity were used. Presented results show high model accuracy, applicable for optimization of real time building operation.

This chapter discusses the vapour compression-based refrigeration systems and describes the operation principle and theoretical thermodynamic cycle of them, the types of refrigeration compressors, the ecological refrigerants and some recovery possibilities of the thermal energy produced by refrigeration systems. Additionally, a computational model for optimal design of refrigeration insulations on flat and cylindrical surfaces and another for refrigeration columns for soil freezing operating with gaseous refrigerant, as well as an experimental study on the frost self-protection of cooling towers on an air-conditioned stand using a vapour compression-based refrigeration system are presented. Finally, an investigation of the energy efficiency of conventional air-conditioning systems in office buildings is included. For this application, an air–water mist cooled system for the air-cooled chiller is proposed. The results of the experiments showed that the most efficient ventilation and air-conditioning system for office buildings consist of an air handling unit and fan coil units with an air–water mist cooled chiller and a cooled water temperature of 8 °C.

The focus of the study is the analysis and sizing of the air conditioning system on board the vehicle which operates in thermal transient for the duration of the typical mission, using “fan coil” type air conditioning devices powered by a hot or cold heat vector fluid loaded into “electro-thermal” charging station and the related ground cogeneration plant (at the BUS terminus). For winter air conditioning, it was assumed that a heat transfer fluid at a temperature of 90 ° C could be stored on board. This value allows the use of water as a heat transfer fluid without pressurizing the systems, minimizing costs and supply problems, and is compatible with the characteristics of ICE cogeneration systems. For summer air conditioning, it was assumed that ice or fluid at a temperature of -20 ° C could be loaded. Also in this case it was decided to operate with a common fluid, such as a solution of water and salt (e.g. calcium chloride CaCl2). A comparative analysis of two solutions was carried out: the first involves the standard solution with BUS air conditioning system with heat pump powered by traction batteries charged by the grid and the second one analyzes the use of a high temperature Fuel Cell in a trigenerative configuration with refrigeration unit absorption fueled by the fumes of the FC. The trigeneration plant produces 100 kW of electricity via SOFC (Solid Oxide Fuel Cell) and, through an exchanger, water at 95 ° C which is stored on board the BUS for winter heating and feeds an absorption refrigeration machine that produces fluid at a temperature of -20 ° C for summer conditioning. For the two solutions, the savings of non-renewable primary energy and the reduction of GHG emissions compared to the standard solution (recharging the electric BUS from the network with on-board air conditioning powered by the traction batteries) are calculated through a WTW analysis. Consumption and emissions of electric powertrains, potentially for consumption and zero emissions, are closely linked to the methods of production and distribution of electricity.

TRNSYS Software is a flexible tool for dynamic simulation of plants, interconnecting the different components of the system represented as black boxes and called “Types”. This paper presents a novel Type for the simulation of a reversible water-to-water heat pump that is freely released. Differently from the previous models available in this environment, the Type is based on the polynomials of the compressors and contains an internal link to REFPROP to easily evaluate the thermodynamic properties of refrigerant fluids. In the present work, the Type was employed for investigating a ground source heat pump providing space heating and cooling to a historic building, where, for architectural limitations, the existing high-temperature terminal units cannot be replaced. Its operation, using different refrigerants, was evaluated under three climates, simulating two heat pump configurations coupled with radiators or fan coils. In the first case, a cascade-cycle configuration was considered to supply high-temperature heat, whereas, with fan coils, a standard single-stage cycle was studied. The results for the cascade-cycle configuration showed a seasonal coefficient of performance ranging from 2.48 for the coldest location (Helsinki) to 2.86 for the warmest one (Athens). These values increased to 3.29 and 4.90, respectively, when considering fan coil terminal units instead of radiators. On the other hand, the seasonal efficiency values were equal to 7.95 in Helsinki and 5.56 in Athens. Moreover, the low incidence of the thermal drift effect on the long-term performance of the cascade ground source heat pump was highlighted, showing for the coldest location a penalisation of 2.5%, compared to 7.3% of the single-stage cycle.

Due to the increasing spread of residential heating systems electrically powered, buildings show a great potential in producing demand side management strategies addressing their thermal loads. Indeed, exploiting the intrinsic characteristics of the heating/cooling systems (i.e. the thermal inertia level), buildings could represent an interesting solution to reduce the electricity peak demand and to optimize the balance between demand and supply. The objective of this paper is to analyse the potential benefits that can be obtained if the electricity demand derived from the heating systems of a building cluster is managed with demand response strategies. A simulation-based analysis is presented in which a cluster of residential archetypal buildings are investigated. The buildings differ from each other for construction features and type of heating system (e.g. underfloor heating or with fan coil units). By supposing to be able to activate the energy flexibility of the single building with thermostatic load control, an optimized logic is implemented to produce programmatically an hourly electricity peak reduction. Results show how the involvement of buildings with different characteristics depends on the compromise that wants to be achieved in terms of minimization of both the rebound effects and the variation of the internal temperature setpoint.

HVAC systems are utilized to construct a thermally comfortable environment for occupants. As people spend more than 90% of time indoors, thermal conditions of indoor environment constructed by HVAC systems demand precise assessment. Predicted mean vote (PMV), a synthesized index, can reveal thermal conditions by evaluating occupants’ thermal sensations. Four environmental parameters affecting PMV: air temperature, air speed, radiant temperature and relative humidity. This study integrates CFD simulations and wireless-sensor measurements to assess distributions of PMV considering radiation models. The distributions of environmental parameters: velocity, temperature, radiant temperature, inside an office room with fan coil unit (FCU) are firstly presented. Based on these distributions, spatial profiles of PMV are obtained to intuitively illustrate thermal conditions. Combined with experimental database collected by thermal-flow wireless-sensors, CFD simulations offer detailed predictions of indoor airflow and thermal parameters. The mean temperature at occupied zone is 23.3 °C agreeing well with set-point temperature 23 °C. Furthermore, velocity values are below draft sensation limitations. The distribution of PMV indicates the cooling system is capable to construct thermally comfortable environment for occupants as well as the draft sensation conforming the satisfactory status. The research outputs provide useful information for designers of cooling system to build a comfortable indoor environment.

Due to the increased awareness of issues ranging from green initiatives, sustainability, and occupant well-being, buildings are becoming smarter, but with smart requirements come increasing complexity and monitoring, ultimately carried out by humans. Building heating ventilation and air-conditioning (HVAC) units are one of the major units that consume large percentages of a building&rsquo, s energy, for example through their involvement in space heating and cooling, the greatest energy consumption in buildings. By monitoring such components effectively, the entire energy demand in buildings can be substantially decreased. Due to the complex nature of building management systems (BMS), many simultaneous anomalous behaviour warnings are not manageable in a timely manner, thus, many energy related problems are left unmanaged, which causes unnecessary energy wastage and deteriorates equipment&rsquo, s lifespan. This study proposes a machine learning based multi-level automatic fault detection system (MLe-AFD) focusing on remote HVAC fan coil unit (FCU) behaviour analysis. The proposed method employs sequential two-stage clustering to identify the abnormal behaviour of FCU. The model&rsquo, s performance is validated by implementing well-known statistical measures and further cross-validated via expert building engineering knowledge. The method was experimented on a commercial building based in central London, U.K., as a case study and allows remotely identifying three types of FCU faults appropriately and informing building management staff proactively when they occur, this way, the energy expenditure can be further optimized.

For the reduction of the electricity cost for cooling buildings in hot climate zones, thermal energy storage at low temperature using phase change materials is a potential solution. The storage medium can be cooled during periods of low electricity cost and then absorb the cooling load any time of the day. In this study, an experimental cold thermal energy storage system using organic phase change materials (A9 and A14) with melting temperature of 9 or 14 °C is investigated. The system is designed for real application conditions coupled with a heat pump which cools down the organic material through the circulation of water in the pipes and fan coil units which dissipate their thermal load in the initially cooled storage medium. It comprises of a thermal energy storage tank, inside which is positioned a staggered heat exchanger with finned tubes immersed in phase change material. The results from the experiments yielded shorter process duration (for both melting and solidification) and higher heat transfer rate when the feed rate was higher. Moreover, the temperature of the water entering and exiting the tank is more than 5 °C for A9 organic material for more than half the capacity of the tank thus, using A9, the fan coil units can operate efficiently for a long time. The heat transfer rate exceeds 5 kW for 32 and 24 min using A9 and A14 respectively and the thermal load that the tank can absorb from the fan coils is above 6 kWh per tank. During the heat pump operation, A9 results to a more constant water outlet temperature over the time compared to A14 which in addition is not affected significantly by the water flow rate. Moreover, the staggered heat exchanger transfers less than 10 kW of heat when the water outlet temperature ranges between 5 and 10°C, a power value which can easily be provided by a typical commercial heat pump.

The aim of this paper is to demonstrate a new algorithm for Machine Learning (ML) based on Gaussian Process Regression (GPR) and how it can be used as a practical control design technique. An optimized control law for a nonlinear process is found directly by training the algorithm on noisy data collected from the process when controlled by a sub-optimal controller. A simplified nonlinear Fan Coil Unit (FCU) model is used as an example for which the fan speed control is designed using the off-policy Q-learning algorithm. Additionally, the algorithm properties are discussed, i.e. learning process robustness, Gaussian Process (GP) kernel functions choice. The simulation results are compared to a simple PI design based on a linearized model.

To solve the severe air pollution problem, Chinese government presented proposals of the electrical heating substitute of the coal combustion for warm. The heat pump is the most economic electrical heating utility. From the start to steady operation of a heat pump, its electrical power is changed with the transient temperature rising of the heated room. Thus, the study of the transient room temperature rising is crucial to evaluate electrical power change of the heat pump. This paper presented a novel numerical simulation method to simulate transient temperature rising of a HVAC room. In this method, velocity of hot air blown off by a fan coil was not constant as usually was, and it was changed with the transient room temperature. This novel simulation method can simulate the real room heating process. The 3-dimensional transient room temperature model was built in a commercial software Fluent. Velocity of hot air blown off by a fan coil was the boundary condition of the model. Hot air velocity was first calculated by the lumped parameter method (LPM), and then it was applied as initial boundary condition of the transient room temperature model. Using this method, the transient temperature rising of a HVAC room was simulated under different outdoor temperatures. Before the heat pump started, the room temperature was assumed to be 3℃ higher than the outdoor temperature. The room was heated until its temperature reached the required temperature. Then, the heat pump steps into the operation state. The time-history of the room temperature from start to steady operation of the heat pump are obtained and analyzed. The results show the novel method can expedite the computation speed. For each time step, the results converged only after 2~3 iterations.

Condensers are extensively used in refrigeration, air-conditioning and power generation systems. Condenser for the solar assisted geothermal cooling system is designed by using software simulation of condenser’s geometrical and flow parameters. The geothermal cooling system is designed to reduce electricity consumption of compressor during peak hours during the summer period in hot weather condition. The subsurface temperature of the earth around 5–6-m depth is fairly constant throughout the year which fulfills the requirement of cooling inside the building or residence by using water as a heat exchanging medium. Water is circulated in closed loop system buried into subsurface which sinks the heat of refrigerant from condenser inside the subsurface soil. The condenser is designed by comparing results obtained from (1) manual calculation (2) simulation by CHEMCAD software. In order to have a good and optimized design, manual and software-based calculations should be carried out simultaneously and verified with each other. It is found that results obtained from both calculations are approximately same with a minor difference. The geometry and flow parameter of the condenser is determined on the basis of surrounding temperature. The solar panel is used for power generation to reduce electricity consumption by the compressor, pump, and evaporator fan coil. This provides the hybrid solar assisted geothermal cooling system.