Cooling Coil Research Articles

Mathematical modelling of passive displacement dual cooling coil (PDDCC) system in a tropical climate

Unlike the conventional displacement ventilation (DV) systems, the Passive Displacement Dual Cooling Coil (PDDCC) system generates airflow in indoor environments based on natural convection and eliminates the necessity of mechanical ventilation to meet the thermal comfort and indoor air quality requirements. Investigations on such PDDCC systems, though, have been largely limited and its performance capacity and fluid flow behaviour are not fully understood. A mathematical model was, hence, developed in the current study to explore the effects of various boundary conditions on the performance of the PDDCC system. Results obtained from the mathematical model were, first, compared and validated against the measurement readings gathered from an experimental investigation conducted on the PDDCC system in a controlled test environment. The validated mathematical model was then applied to a parametric evaluation where the effects of chilled water supply (CHWS) temperature, flow rate, and return air temperature on the PDDCC system performance were examined. The varying effect of the latent and sensible cooling load was observed at the different boundary conditions applied to the PDDCC model. Slightly more than 32% of rise in total cooling load was predicted by reducing the CHWS temperature which established a much more significant contribution in comparison to the CHWS flow rate which generated approximately 5% rise in the total cooling load. Findings were supported by examining the sensible heat ratio (SHR) and the ratio of Latent cooling load: Sensible cooling load which was then was attributed to the temperature difference between the supply and return air temperature. By ensuring the maximum temperature difference, the total cooling load performance of the PDDCC system can be maximised. The contribution of both the CHWS temperature and flowrate was essential to achieve the maximum cooling load, hence, improving the total cooling performance of the PDDCC as a result.

Experimental investigation of the cooling capacity and thermal performance of the passive displacement dual cooling coil system in tropical climate

This paper focuses on the application of Passive Displacement Dual Cooling Coil (PDDCC) system in an indoor space based on a test lab. Parametric study, first, was carried out using Computational Fluid Dynamics (CFD) simulation to identify the optimum fall duct design for the PDDCC unit. Thermal profiles obtained through the simulations indicated that the fall duct with 300 mm height and 0° taper angle was most suitable as it generated the largest volume of cool air which sufficiently cooled the space. It was then applied to the experiment of the PDDCC units in the test lab to study the system's thermal performance. The total cooling load removed by the two PDDCC units within the indoor space varied from 2.24 kW to 2.93 kW. The latent load removal over the entire experiment duration ranged from 0.7 kW to 1.35 kW where the highest latent heat was removed at the lowest chilled water setpoint temperature of 7.5 °C. Thermal stratification trends displayed that temperature within the room for all chilled water setpoint temperatures (7.5 °C, 8.5 °C, 9.5 °C, and 10.5 °C) corresponded with the increase in heat load within the indoor environment. The humidity level above 1 m ground level was not exceed 56%. The PDDCC system was found to have excellent latent heat removal capability. The PDDCC system was able to produce a thermally comfortable environment for 67% of the experimental permutations. The low humidity level within the test cell allowed to raise the boundary of the acceptable temperature range for achieving human thermal comfort to as high as 26.5 °C.

Cooling Thermal Comfort and Efficiency Parameters of Ceiling Panels, Underfloor Cooling, Fan-Assisted Radiators, and Fan Coil

Climate change has brought a compelling need for cooling living spaces to the attention of researchers as well as construction professionals. The problem of overheating enclosures is now exacerbated in traditionally affected areas and is also affecting countries that were previously less prone to the issue. In this paper, we address measurements of thermal comfort and cooling emission efficiency parameters for different devices: ceiling panels, underfloor cooling, fan-assisted radiators, and fan coil. These devices were tested in low and high cooling capacities of up to 40 W/m2 while also featuring heating dummies to imitate internal heat gains. Air temperatures were measured at different heights, allowing to evaluate the thermal stratification with high accuracy. Thermal comfort differences of the tested systems were quantified by measuring both air velocities and operative temperatures at points of occupancy. In summary, the best-performing cooling devices for the studied cooling applications were the ceiling panels and fan radiators, followed by underfloor cooling, with a limitation of stratification. Because of the strong jet, fan coil units did not achieve thermal comfort within the whole occupied zone. The results can be utilized in future studies for cooling emission efficiency and energy consumption analyses of the different cooling devices.

A simulation study of radiant chilled ceiling with dedicated outdoor air system for office buildings in Thailand

Radiant chilled ceiling (RCC) integrated with dedicated outdoor air system (DOAS) has been considered as a system offering building occupants a good thermal comfort with energy efficiency. This paper compares three different configurations of RCC and DOAS system in terms of cooling load, room condition and energy consumption. The results from TRNSYS simulation presented that all the configurations could maintain the indoor condition with the Predictive Mean Vote (PMV) value ±0.5 over the office hours 6:00-18:00. The mean radiant temperature of the room was found below the room air temperature which resulted from the low RCC surface temperature of around 19°C. No condensation occurred on the panel during the system operation. The study showed that the RCC with DOAS comprising of cooling coil (CC), round around coil (RC) and enthalpy wheel (EW) is the most energy saving configuration.

基于Deform软件的铜冷线圈热处理工艺的模拟研究

基于Deform软件的铜冷线圈热处理工艺的模拟研究

Improving Efficiency of Cooling Coil Chiller Units

Air Cooled condensers were first introduced in US power industry in early 1970’s, but only during last 10-15 years number of installations greatly increased largely due to growing attention being paid to environmental safety. Also, growing demand for water for both domestic and industrial use has brought an increased interest in use of Air Cooled condensers. This is a review paper which studies the performance of Air-cooled condenser under various operating conditions it is found that there is degradation in performance of air cooled condenser under high ambient temperatures and windy conditions. The heat rejection rate of ACC also depends on surface condition of fins and thus its performance is reduced due to external fouling of finned tubes due to weather conditions and by internal fouling from condensate (Ammonia corrosion). A Hybrid (dry/wet) dephlegmator achieves major enhancement in performance when ambient temperatures are high. Also shading of condensers is done for air-conditioning units to mitigate the adverse effect of high ambient temperatures due to solar radiation. Now a day’s wind walls are used to reduce the effect of high wind velocity .second option is to increase the fan speed Fin cleaning plays an important role in heat rejection. External cleaning improves air side heat transfer coefficient. In order to improve the performance of an ACC Flat tubes inclined at some angle to horizontal can also be used in place of conventional circular horizontal tubes so that an improvement in heat transfer rate occurs.

Cooling Load and Exergy Destruction Analysis in Air Conditioning Operation Room with Ambient Temperature Variation

HVAC installations are essential to the operating room to maintain the safety of environmental conditions and provide comfort for patients and medical personnel. Operating room is a room with a class of 10,000 where the maximum number of particles in the room is 352,000 particles per cubic feet for bacteria 0.5-micrometer size (ISO 14644-1). To achieve the desired air conditions in the operating room required an air conditioning tool that is Air Handling Unit (AHU). The AHU determination shall be adjusted to the cooling load of the chamber derived from the sensible load and latent load. Exergy analysis is required to optimize a process and evaluate the device performance. The purpose of this study is to calculate the cooling load and perform the analysis of exergy destruction on Cooling Coil and Electric Heater in AHU. The calculation of cooling load uses the standard air change method. Exergy analysis uses the second law of thermodynamic concepts related to entropy. The results obtained cooling load and exergy destruction increases with the increase of ambient temperature. Maximum exergy destruction in cooling coil 1 and 2 at 35°C is 3.3 kW and 1.6 kW while in the electric heater is 0.52 kW.

An Optimum Control Method for HVAC Systems with Double Circuit Cooling Coil Using Particle Swarm Optimization Algorithm

Double circuit cooling coil (DCCC) is a special type of coil which could adjust the chilled water flow rate and the chilled water temperature independently. In this study, a particle swarm optimization (PSO)-based method is proposed to optimize the chilled water flow rate and the chilled water temperature. A test HVAC system with DCCC is constructed in laboratory firstly. The system is modeled by first principles, including a coil model, a heater model and a humidifier model. The parameters of the models are calibrated using measurements from the real system. Results show that the simulated data fit the experimental data very well. The real-time optimal parameters for controlling the DCCC are obtained using PSO-based method. The energy performance of the PSO-based method is analyzed. The most significant energy saving potentials could be obtained with energy saving potentials above 60% under high-sensible heat loads and low-latent heat loads.

Ultraviolet germicidal coil cleaning: Impact on heat transfer effectiveness and static pressure drop

Cooling coil surfaces are ideal sites for biofilm formation due to the presence of adequate nutrients (deposited particles) and moisture (condensate), causing adverse impacts on heating, ventilation and air-conditioning (HVAC) energy usage and performance. In this study, an HVAC test apparatus was built in our laboratory to investigate the hypothesis that ultraviolet germicidal coil cleaning (UVG-CC) of heat exchanger surfaces improves heat transfer effectiveness and reduces the static pressure drop across the coil. The test apparatus consisted of two parallel ducts, each with its own cooling coil. One coil was treated with UVG-CC while the other was the control and left untreated. Thermodynamic properties of the air and water flowing through both heat exchangers were monitored over the course of two years with sensors and a data acquisition system. Differences in static pressure drop and coil effectiveness between the UV-treated and control coil were compared across multiple modes of coil operation (defined by presence of condensate). The effectiveness of UVG-CC was drastically affected by the presence of condensation on coil fins. We observed a statistically significant difference in the heat transfer effectiveness between the UV-treated and control coils in wetted conditions while no difference was observed in dry conditions. Sensor accuracy, however, contributed to large uncertainty in our result. The average heat transfer of the UV-treated coil was 3.0–6.4% higher compared to the control coil, with an uncertainty of ±2.7%. UVG-CC, however, did not significantly reduce static pressure drop.

Modeling and Analysis of Cooling Coil for Control System Design Using Gray Box Approach

The purpose of the study is to design a method analyzing dynamic behavior of cooling coil in order to be applicable in online simulations. Coils account for the highest energy consumers among other components in an Air Handling Unit (AHU). Essential data as input-output of neural network is provided using energy and mass conservation equations. An implicit numerical method is used to solve dynamic equations of coil. The results of mathematical methods are applied in the output of neural network to design an online model. The proposed model is based on an active coil used in Heating, Ventilation and Air Conditioning (HVAC) systems of clean rooms in Iran Pasteur Institute. Since in active air handlers, input and outputs are not measured, here we model air conditioning systems generally. The results in comparison with actual system data indicate an acceptable performance of the proposed method, so that combination of numerical results with a nonlinear autoregressive exogenous model (NARX) makes it possible to control system effectively by saving a significant amount of time.

Ultraviolet germicidal coil cleaning: Decreased surface microbial loading and resuspension of cell clusters

Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation due to the presence of adequate nutrients (deposited particles) and moisture (condensate). In this study, a heating, ventilation, and air-conditioning (HVAC) test apparatus was built consisting of two parallel ducts, each with its own cooling coil. One coil was exposed to ultraviolet germicidal coil cleaning (UVG-CC) while the other was the comparison control to investigate the impact of UVG-CC on surface microbial loading and bacterial attachment. Surface samples were collected by swabbing a uniform area of coil surface and airborne samples were collected isokinetically with sterile funnel filters. All samples were quantified via direct epifluorescent microscopy. Prior to irradiating, higher concentrations of surface microbial loading were found on the downstream side of both cooling coils under condensing conditions. Conversely, under dry surface conditions with downstream UV irradiance, surface concentrations were higher upstream. UVG-CC (at an average 200 uW/cm2 on the coil surface) reduced surface microbial loading by 55% on average during condensing conditions and inhibited bacterial attachment causing clusters of bacterial matter to become airborne downstream of the cooling coil. Additionally, it was found that desiccation also inhibited surface microbial loading and yielded cluster detachment but to a lesser degree than UVG-CC treatment.

Optimum Conditions for the Efficacy and Safety of Cryofiltration Apheresis: An Analysis of Circuit Temperatures Depending on Plasma Flow Rate and Cooling Coil Lengths/Turns.

A system providing both appropriate cooling and warming are needed for the efficacy and safety of cryofiltration (CF) plasmapheresis. We measured some points of CF circuit temperatures with varying plasma flow rates (QP = 10-40 mL/min) and the numbers of connecting cooling coils (one or two) under the conditions of blood flow rate (QB ) 100 mL/min with 7700-mm coil length, 19 turns, and 50-mL priming volume. We measured the respective temperatures of each point of starting/returning for an extracorporeal circuit (TA /TV ), intracooling coil (TC ), and post-plasma fractionator (PF) (TPF ). The subtraction of TV from TA (ΔT) was used as an indicator of safe return. There were no significant differences in TC , TPF , or ΔT in accordance with each QP between that of one and two coils. All of the Tc values under the condition QP ≤ 20 mL/min achieved <4°C. The TPF under the condition QP ≥ 20 mL/min was not significantly different compared to that of QP 30 mL/min (the lowest condition). Although the ΔT increased depending on the QP increase, the ΔT under the condition QP ≤ 15 mL/min was not significantly different from that of the control (one-way double-filtration plasmapheresis [DFPP]) group. We conclude that (i) one coil is enough for effective cooling in CF, and (ii) an ideal QP that fulfills the required conditions for both effective cooling and sufficient warming of returning fluid does not exist, but QP from 15 to 20 mL/min may be a relevant range.

Optimisation of Direct Expansion (DX) Cooling Coils Aiming to Building Energy Efficiency

Efficient Air Conditioning (A/C) system is the key to reducing energy consumption in building operation. In order to decrease the energy consumption in an A/C system, a method to calculate the optimal tube row number of a direct expansion (DX) cooling coil for minimizing the entropy generation in the DX cooling which functioned as evaporator in the A/C system was developed. The optimal tube row numbers were determined based on the entropy generation minimization (EGM) approach. Parametric studies were conducted to demonstrate the application of the analytical calculation method. Optimal tube row number for different air mass flow rates, inlet air temperatures and sensible cooling loads were investigated. It was found that the optimal tube row number of a DX cooling coil was in the range of 5 - 9 under normal operating conditions. The optimal tube row number was less when the mass flow rate and inlet air temperature were increased. The tube row number increased when the sensible cooling load was increased. The exergy loss when using a non-optimal and optimal tube row numbers was compared to show the advantage of using the optimal tube row number. The decrease of exery loss ranged from around 24% to 70%. Therefore the new analytical method developed in this paper offers a good practice guide for the design of DX cooling coils for energy conservation.

サーバールームにおける冷媒自然循環型フリークーリングコイルの特性評価 その2 地域ごとの比較

サーバールームにおける冷媒自然循環型フリークーリングコイルの特性評価 その2 地域ごとの比較

Dehumidification and Temperature Control for Green Houses using Lithium Bromide Solution and Cooling Coil

Dehumidification and Temperature Control for Green Houses using Lithium Bromide Solution and Cooling Coil

Design Optimization of the Cooling Coil for HVAC Energy Saving and Comfort Enhancement

This article investigates and recommends design improvements of cooling coil geometry contributes for a central cooling system by using a simulation‐optimization approach. First, theoretical–empirical system models including mechanistic relations between components are developed. An actual central cooling plant of a commercial building in the hot and dry climate condition is used for experimentation and data collection. Available experimental results were compared to predicted results to validate the model. An algorithm was created in a transient system simulation program to predict the best design. Then different new designs for cooling coil were constructed to evaluate the potential of design improvements. Afterwards, the computer model was used to predict how changes in cooling coil geometry would affect the building environment conditions and the energy consumption of heating, ventilating, and air‐conditioning components. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1209–1216, 2013

System Identification of a Cooling Coil Using Recurrent Neural Networks

Modelling a non-linear plant by employing first principles is a tedious task and the resulting model often does not replicate the true behaviour of the plant. The cooling coil of an air-handling unit exhibits severe non-linearity and it is difficult to develop a first-principle model which can replicate the true plant behaviour. The paper discusses the modelling of a cooling coil of an air-handling unit using first-principle approach as well as artificial neural networks. In order to capture the dynamics of the cooling coil, a type of recurrent neural network, i.e. non-linear autoregressive network with exogenous input (NARX) is used. It has been demonstrated that a recurrent neural network with sufficient training has better performance as compared to the model obtained using first principle.

Performance study of a constant temperature and humidity air-conditioning system with temperature and humidity independent control device

To reduce the large energy penalty for constant temperature and humidity control in conventional air-conditioning systems, a novel temperature and humidity independent control (THIC) device is developed for typical cooling coils. The working principle of the THIC device is to adjust the chilled water flow rate in a cooling coil (CC) to maintain constant temperature and to adjust the apparatus dew point temperature of the CC to maintain constant humidity. A split-range control strategy is developed to control the cooling coil with the THIC device, the heater and the humidifier to achieve reliable control of indoor temperature and humidity while minimizing energy use.Control performance of the THIC device was tested in an existing constant temperature and humidity air conditioning system serving a storeroom in a museum. The field test shows that the indoor temperature and humidity were well controlled in the required range. Energy performance of the THIC was tested using simulation tests on TRNSYS platform. Seven testing cases with different typical load conditions were conducted. The energy performance of the THIC is compared with conventional air conditioning systems. The results show that the THIC device can achieve power saving of 30–50%.

A museum storeroom air-conditioning system employing the temperature and humidity independent control device in the cooling coil

Abstract For conservation of cultural heritage, HVAC systems are often necessary for museums to maintain suitable indoor environment with precise control of indoor thermal-hygrometric parameters and air velocity. Large deviations of these parameters from the design values should be prevented, because they may cause degradation of artworks. So, more energy consumption is inevitable. This paper presents a novel temperature and humidity independent control (THIC) device and its associated control method in a museum storeroom air-conditioning system. Compared with the conventional HVAC system with the cooling coil (CC), where the apparatus dew point is usually fixed, this system adopting the THIC device can achieve independent temperature and humidity control in an energy saving way. The experiment study shows that this system can reduce the energy consumption by 21.7%, compared with the conventional HVAC systems using reheat and humidify for an indoor thermal-hygrometric environment, and the temperature and humidity in the storeroom are also kept stable and at a higher precision level.

Detecting Cooling Coil Fouling Automatically—Part 2: Results Using a Multilayer Perceptron

A new concept to automatically detect cooling coil fouling is introduced in a companion paper (Veronica 2010). The concept maintains a data-driven dynamic model of the cooling coil on-line with coil instruments, so all steady and transient coil behavior is assimilated. The fouling surveillance is to periodically apply a specific transient sequence (the query) to this model off-line as a surrogate for applying such a test to the real coil. A query sum, calculated from the transient response of the model to a query, is used to detect changes in the real coil, to discern fouling from other faults such as instrument drift, and to further discern water-side from air-side fouling. A crucial element to viability of the concept is that the data-driven coil model respond to queries dynamically and recursively, with sufficient stability and accuracy so that fouling can be discerned. Yet, the model should be of reasonably simple architecture, permitting a plausible embedded implementation. Based on trials using simulator data, a relatively simple, three-node, multilayered perceptron demonstrates sufficient accuracy and stability so that the concept can be regarded as viable and as warranting further development. Also presented are the factors found to be critical for dynamically employing a data-driven model of any architecture to detect process faults.