Heating, Cooling, and Air-Conditioning (HVAC) Systems
INTRODUCTION:
Building Science Corporation (BSC) hopes to gather useful information on the performance of energy-efficient technology packages produced by a manufacturer in a tropical environment by conducting advanced testing of new building power packages in Texas. This research focuses on a few important gaps and barriers: (Alenezi,2017).
• Competitive and repeatable designs for acquiring pipelines inside a specified environment by a production builder; and
• Complete high-performance technology packages that will be compatible with future code changes.
The BSC plans to collect data on:
• Cost and usage of issues by installing the whole heating, ventilation, and air conditioning (HVAC) system in a well-ventilated location in the production rooms.
• A comparison of the many energy-saving approaches available in the industry (energy efficiency vs the Building America (BA) Benchmark versus site energy savings given by frequently used home modelling software).
This pilot community project’s suggested technology bundle is best suited for isolated single-family production houses. The Houston package is scientifically appropriate for other tropical producing locations. This study’s findings on the deployment of a technology package on the size of a productive community, as well as long-term performance data from the housing community, will help to expand the distribution of this package to new houses throughout the tropical environment. The study project’s immediate impact will be to inform the work of David Weekly Homes (DWH) – Houston. Lessons acquired in the economics of design and construction variation can be applied to a production builder’s future business model. The revised 2012 International Energy Conservation Code (IECC) greatly minimises the operational gap between code-built and built-in dwellings in terms of meeting energy efficiency criteria. (Alghoul,2017).
The obligatory installation of the whole HVAC system in an ecologically friendly setting is a fundamental component of the 2012 IECC. This authority obligates builders to create low-cost pipeline systems within thermal enclosures. The project may also help to BA measuring criteria by reducing redundancy and increasing the cost effectiveness of projects that will not only satisfy the existing energy code, but will also meet the projected development code in the future. This is an excellent chance to analyse the importance of a low-cost pipeline system within a specific setting so that makers of production houses may always compete in the market. There is also a chance to assess whether housing developments will satisfy the interim mission of the 2015 IECC. DWH sees this as part of the second long-term plan for keeping a highly efficient design that adheres to existing code requirements. (Smith,2017).
This effort will also give valuable design and construction data for other hot-humid environment production builders, as well as local Home Energy Rating System (HERS) raters and architects.
OVERVIEW:
A process is defined as “a sequence of activities (tasks, steps, events, tasks) that gather input, add value to it, and produce output (product, service, or information) for the client.” To preserve the company’s competitive edge and satisfy consumer expectations, an effective and efficient procedure is required. The process map is a visual assistance for comprehending unseen labour processes. This diagram depicts the connections between functions, inputs, and outputs. The process model in this thesis refers to a collection of map sequences, each with a thorough description. The mapping / modelling process may identify the beginning and ending points of events in a business process, as well as share information between activities and choices made in a business process. A visual representation of a process can aids in process comprehension. Furthermore, inefficient functions may be identified easily using the process model. Tasks that cannot be properly recognised, examined, and connected together cannot be questioned, and so cannot be improved or perfected, just as immeasurable tasks cannot be managed. The first concept is that a process model should have strong process visibility so that process participants may see its role just by glancing at a process model. The second purpose is to partition relationships and dependencies across activities to promote appropriate managerial effort.
The third objective is for the process participant to comprehend other role-players who have information flowing via their activities.(Ishak,2017)
• Program Implementation: A process model aids in determining what to do next, assessing progress, integrating delivery, and analysing the effects of change and the number of alternatives available.
• Foundation for Sustainable Development: A process model can assist in analysing prospective policy adjustments based on total value (investment costs against extra value advantages) and identifying issue sources.
• Information retention and learning: When a process does not perform as planned, the process model can help capture lessons gained. The process model might also be used to generate common names for tasks, deliverables, and collaborations.
• Visualization: A process model allows individuals to see where they are in the process, what they need and should create, and when they should produce it. It serves as the foundation for strong, dedicated, and accountable collaboration across organisations, groups, individuals, and even businesses.
• Training: A process model may assist new workers in understanding what they need to accomplish and why, as well as directing them to further resources.
OBJECTIVES:
The goal of this research is to create a process model that specifies the design process for retrofit heating and air conditioning (HVAC) systems for use in an integrated delivery system. The following objectives were pursued in order to reach this goal: (Khor,2019)
• Creating HVAC design process maps for common restoration projects;
• Recognizing incoming information and the outcomes of HVAC design activities;
• A more refined process model for use in an integrated design process; and
• Validate process maps through conversations, workshops, and case studies.
LOAD CALCULATIONS:
The primary goal of the building and its HVAC system is to create appropriate interior conditions for occupants’ well-being. Inadequate home circumstances have an impact on occupants’ health, productivity, and comfort. Poor indoor air quality reduces productivity and increases absenteeism in office buildings. This may be prevented by investing sufficiently in creating and maintaining a more comfortable home environment. The literature on the impact of the domestic environment on health and productivity discovered a strong correlation between: air intake and temporary sick leave, air quality and productivity, visual and productive air quality, temperature and production, and temperature and sick building syndrome symptoms. It is obvious that special consideration should be given to the comfort of the interior heating system and the purity of the indoor air. As a result, many national and international regulations establish low costs that fulfil interior thermal comfort and air purity. Aside from interior conditions, the advantages of indoor heating are another essential feature that adds greatly to energy consumption, both directly, through lighting and loading equipment, and indirectly, through influencing heating and cooling loads. It might be a primary reason why cooling systems are installed in office buildings in colder locations, such as the United Kingdom. (Ma,2019)
The following are the primary sources of advantages for indoor heating:
• Residents,
• Electronic office equipment, and
• Lighting that is active.
The benchmark values for internal heat benefits are mostly based on limited data gathered from many surveys of various sorts of features and functions. If quantitative data is not available, the most frequent method of calculating the advantages of indoor heating is to utilise applicable pricing based on experience, which is considered acceptable industrial practise. (Meyer,2019)
By utilising daylight management, the benefits of indoor heating, particularly from artificial lighting, may be mitigated. Many of the impacts of direct sunshine on energy savings are documented in the literature. Saving energy for electric lighting and cooling is an easy method to measure. In their study, which was based on a typical Hong Kong office building, daylight was able to maintain an adequate level of interior illumination by around 40% to 60% of the time, resulting in a 50% decrease in the usage of artificial lighting and an extra 11%. Instead of cooling, use a coefficient of performance (COP) 3 to save energy. The same authors conducted field observations on numerous entirely cold air-conditioned cell phone workplaces, which appear to be the polar opposite of managing sunshine and outside lighting. Estimates show that energy savings in processed lighting may be as high as 50% in circuit workplaces. According to comparable research, the savings percentage was significantly lower in the open airline office space, averaging 33 percent. (Risbeck,2021)
PROJECT DOCUMENTATION:
ASSUMPTIONS:
(1) Minimize the number of fittings.
Fittings are costly and cause substantial pressure loss as compared to straight duct.
(2) Use semi-extended plenums.
Plenums minimise the number of transition fittings required and make balance easier.
(3) Seal ductwork.
Table 1 shows the standard duct sealing criteria. Table 2 depicts air leakage from unsealed ductwork longitudinal seams. Longitudinal seam leakage in metal duct accounts for 10 to 15% of overall duct leakage.
(4) Use round duct.
Round duct has less friction loss than rectangular duct for a given perimeter.
(5) Reduce aspect ratio.
Fittings are costly and cause substantial pressure loss as compared to straight duct.
DEVELOPMENT OF THE OVERALL MODE:
Smaller facilities are frequently constructed to house more heat-generating equipment in one big open space, such as engines, generators, switchgear, and buses. Because of the simplicity of the air distribution system and the essential controls, the HVAC system for this type of plant is simple to design. Larger plants sometimes include a service area as well as areas for several machines, stores, offices, control rooms, lunch rooms, and so on. Because several devices might work at various temperatures, rooms must have the same ambient design criteria and may be served by a single HVAC unit. Some rooms, such as uninterrupted power supply (UPS), communications, office, and control rooms, have varied ambient needs and may require separate HVAC equipment to be adjusted.(Rosli,2019)
Plants are often organised into units, with each area corresponding to the serving of the construction necessary for the component. Dependent on the plant outline, heat and refrigeration loads, and required temperature controls, a unit bay may be cooled concurrently with a central air conditioning system, either with a specialised HVAC device or with a combination of a central area with a particular unit of HVAC equipment. Central systems, which may be installed for conventional smoke extraction, will normally maintain the same temperature throughout the facility. When a factory is divided, intermediate systems can become complicated, necessitating the considerable use of open and embedded pipes, fire extinguishers, smoke-reducing materials, and control cutters. (Satrio,2019)
If cool air is required, the following options are usually considered in the following order: air-cooled unit with cold water coils using on-site water (usually limited to temperatures below 65 degrees Fahrenheit [F]); direct evaporative coolers; indirect cooling / direct steam; cold water, and direct expansion coils (DX). Fountain water is another option if there is enough of it. It should be noted that the use of clean (drinking) water to cool HVAC heat-resistant equipment such as condensers is illegal in many areas. (Sultan,2018)
CALCULATIONS:
1)Ceiling temperature (Tc) for room heights (H) less than 20 ft, is given by:
Tc = [1.00 + 0.02h] Tb
Where: h = the room height in feet above the breathing line not to exceed 15-feet,
Tb = the breathing line temperature. The breathing line is measured 5 feet above floor level in ºF.
(2) Average room temperature (Tavg) for room height (H) less than 20 feet is given by:
Tavg = [1.00 + 0.02(H/2 – 5)] Tb
Note: Tavg = (Tc + Tf)/2,
Where: Tf = Floor temperature at h = -5
Stratification is impossible while roof fans are operating, and the temperature differential between the floor and the roof may be minor. The figures (3) and (4) (invented by Jennings) can be used to calculate a conservative medium temperature (at ° F) for big buildings with fan-resistant heat exchangers.
(3) Average temperature (Tavg) for a ceiling height (H) less than or equal to 15 feet is given by:
Tavg = [1.00 + 0.01(H – 5)] Tb
(4) Average temperature (Tavg) for a ceiling height (H) greater than 15 feet is given by:
Tavg = (1.1) Tb + 0.1(H-15)
Column insulation is not required in the winter since the heat delivered to the surface rises to the roof and is lost owing to heat transfer to the roof and higher sections of the wall. Fans of multi-function roofs capable of providing, exhausting, and supplying ambient air give solutions to huge buildings’ separation, cooling, and heating demands. Propeller fans, housing, hoods, filters, and control dampers are all part of these fans. Fans are available as pre-assembled package units with corresponding controls, or they can be incorporated into the needed components. Roof-out ventilators are thermostatically controlled to work constantly in an exhaust mode, where 100 percent external air cools the generator or the vehicle room floor.
RESULTS AND DISCUSSIONS:
An independent database was constructed to assess the capacity of retrospective models to anticipate HVAC system cooling, heating, and auxiliary power requirements. The original database’s various parameters are shared by these authentication database types. They differ from the original records, however, in that they lack fenestration on other walls.
The verification data consists of 1,920 office building models linked to five HVAC systems, as well as construction demand figures. The outcome of the simulation was used to test retrospective models generated from the original database. The statistical parameters in Table 4.26 reflect the equilibrium of the regression models employed in both the original and verification data sets. There are a few occasions where the RMSD of the authentication database exceeds the RMSD of the original database. However, because the discrepancies in RMSDs and residual range are minimal, it can be inferred that sophisticated retrieval models, both single-variable and dual-variable, can estimate HVAC system temperature, cooling, and auxiliary power needs. accuracy.
Four types of HVAC system models were created for the objectives of this study. The first is a variable volume system (VAV), while the second is a constant volume (CAV) system. Both systems are a component of the HVAC air-conditioning system unit and include local heating boxes. A specialised outside air system (FC) and a cooling ceiling system are two storage solutions for air water systems, particularly Fan coil units. The cooling system includes an air conditioner that solely provides fresh air, while the radiator heating system meets the requirement for heat.
CONCLUSION:
The VAV system changes the volume of its source air while processioning the air hoard temperature continuous to match to the decrease of interplanetary consignment during partial load, allowing it to preserve a predefined temperature of the dry bulb area while conserving fans in reduced volume flow. The maximum temperature coils (HC) and cooler (CC) are regulated by the supply air temperature (tsa), which is set at 16 degrees Celsius. Preconditioned air is transported into the space via air-conditioning boxes, where it is heated again if necessary. Each air-conditioning box consists of a soluble coil and hot water, both of which are controlled by a zone temperature (tza) and a damper reversal action. This implies that in hot mode, it begins with a little flow of hot water and a small flow of air. As the load grows, the warm liquid movement increases while waiting for it grasps the extreme flow rate, at which point the air damper begins to exposed to see the consignment.
Unlike the VAV system, the CAV system maintains a constant air movement rate while fluctuating the supply air temperature (tsa) from 16 ° C to 22 ° C to meet the chilling needs of the warmer environment. This method minimises the power of the zone reheat coil and prevents it from overheating. To satisfy the mixed air temperature, an external air mixing box coupled with an inverted air mixer controls the amount of outside air in both systems (tma). Because the feed air supply, which passes through the fan engine, collects the dissipation heat of the fan, the mixed air temperature is roughly one degree Celsius lower than the providing air temperature. When employing an economizer unit, the volume of outside air is augmented wherever feasible to take advantage of unrestricted chilling.
The fan-coil system consists of four pipe tunnels and an air-conditioning unit that delivers 100 percent fresh air, which is adequate to fulfil the fresh air necessities exclusively. To optimise the benefits of free cooling, the fresh air temperature is adjusted to differ the supply air temperature between 16 ° C and 22 ° C. However, due to the comparatively low volume flow rate compared to VAV and CAV systems, free cooling is severely constrained. Each fan coil unit has an air conditioning fan as well as heat and cooling coils. Indoor temperature is meticulous by a local thermostat (tza), which alters the flow of water via a heating or cooling coil in response to local demand. When there is no need to heat or cool, the fan coil fan is turned off. Outdoor air is pre-treated using a heat rescue unit (HRU) with a 65 percent efficiency, which exchanges the temperature between the supplied air flow and the airflow.
The cooling ceiling system consists of the following components: a cold ceiling feature; an air-conditioning unit outfitted with a heat rescue unit that only takes in fresh air (the air side is regulated in the same manner as a Fan-coil system); and radiators to satisfy the requirement for warmth. The cooling area of the set area is extended by 2 ° C due to the manner this system distributes cooling and maintains comfort (partial radiation and partial convection); from 24 to 26 ° C in offices and from 26 to 28 ° C in common spaces. In this work, two types of expanded ceiling elements were investigated: thermally lightweight elements (aluminium panels) and heavyweight applications (cold water pipes embedded directly into concrete ceiling).
In all of the preceding operations, it was assumed that the primary HVAC system was 100 percent efficient and capable of providing enough electricity at the needed temperature to fulfil all requirements at all times. For all tested systems, the temperature of the hot water provided to the basic system was set at 82 ° C, and the temperature of the cold-water supply temperature was set at 7 ° C, apart from in the case of a chilly maximum amount, when it was set at 14 ° C.
