【 Weak current College 】 HVAC design compared to some of the issues

Summary: think design technical and economical comparison is a affect HVAC design quality and efficiency of work. On HVAC design technology economy problems, from feasibility, economic, regulatory, safety and environmental impact analysis, and pointed out that the comparison of the design of some misunderstanding, put forward suggestions.
Keywords: HVAC design technical and economical comparison

Introduction

Design on HVAC project design and bad relationship between the success or failure. In recent years, with the rapid development of science and technology, as well as on energy saving and environmental protection requirements and continuous improvement, HVAC design programme in the new booming, for the same design projects, often can have several, or even dozens of dozens of different design options to choose from, the designers had to do a lot of comparison and selection work, design is becoming the technical and economical comparison affect HVAC design quality and efficiency of an important work. HVAC design scheme for the evaluation of a number of factors, some of the factors is difficult to quantitative expression, many factors are not comparable, each design programmes often has its own advantages and disadvantages, faced with numerous design options, consider the problem of different views of the parties, always different, even quite different. Currently in the design of some of the comparison of disarray that designers do. How HVAC design scheme for comparison and selection of science is HVAC design professionals in the actual design work often encountered in a key technical challenges. Author based in the design, plans and programmes for the assessment of some experience, on HVAC design scheme comparison in some superficial analysis of the issues.

1, feasibility and reliability issues

To meet the requirements, this is the programme feasibility should be considered a major problem. Designs should be consistent with State and local government regulations and requirements, including requirements relating to environmental protection; design should be able to meet the relevant requirements (such as electricity, gas supply, water supply, heating, etc.) and to take into account these conditions for long term, changes in circumstances. Such as the use of water-source heat pump design should consider local geology, groundwater resources of situation and trends, the heat load in winter and summer cooling load imbalance caused by thermal (cold) cumulative effects issues. For parameters such as temperature and humidity higher or special technology of HVAC design project, you should design for the whole year cycle analysis to ensure that its year-round outdoor weather conditions of adaptability. For those unable to use standard equipment of special circumstances, non-standard equipment should be put forward detailed parameters of the request, and the parameter requirements should be reasonable and practicable. Whether there is enough room area is also a feasibility assessment design programme must take account, in particular for some renovation works and the building area is strained. For some requirements as a guarantee for indoor air parameters of important projects, as well as air conditioning system downtime will have a serious loss of places, such as Cosmodrome, consideration should be given to the system of equipment reliability and backup issues system reliability analysis. In this case, the outdoor weather parameters and the determination of the safety factor should also be a special consideration.

2. economic comparison problems

Economic comparison is HVAC plan comparison in considering the issue of a maximum. When comparing the economy first note baseline must be consistent. Should adopt the same design requirements, usage, device classes, energy prices, comfortable situation, beautiful situation, to compare the baseline conditions, so as to ensure that the comparisonof scientific programmes and rationality. If you use brand-name equipment and the use of low quality equipment programme for economic comparison, it is clearly unreasonable; if you do not consider the difference between, on the comfort of a fresh air supply and no fresh air supply economic comparison of programmes is clearly impossible to make the right choice; if you do not consider the appearance and comfort for economic comparison, centralized air conditioning programme was clearly unfair.

Once the investment is the investment side of the main concerns of a parameter in the calculation of the investment should be fully accurate and not leak. HVAC design scheme of an investment not only includes a variety of equipment, pipelines, material investment, and should include all related fees and charges (such as thermal network access fees, electricity equipment MEF, natural gas sources, etc), the appropriate installation and commissioning costs related to the project management and other charges related to water treatment and distribution and control of investment, the engine room construction investment and the cost of the corresponding outdoor pipelines, while those in the actual design work can easily be missed. As a result of the same kind of equipment manufacturers, prices vary, so different when comparing the programme economics computing devices of average prices of price should be used. These are direct costs, in some cases indirectly benefit should also be considered. Such as hotels, restaurants, office buildings in the area of the air conditioning room save as commercial housing can yield benefits. If you take a loan for construction, comprehensive economic comparison you should also consider the loan interest rate and repayment period, and other dynamic elements.

Operating power consumption and operating costs are the HVAC design technical and economical comparison must consider important parameters. Operating power consumption in addition tocalculating HVAC host (boiler and chiller, etc.) of energy consumption, but also calculate other assistive device (such as fans and pumps, etc.) of energy consumption. You cannot simply follow the equipment nameplate power and run time to calculate the energy consumption of the product and should take into account seasonal variations throughout the year, the actual load of the building, taking equipment non-standard State of efficiency. Office building, teaching building, Office building and a swimming pool, and other buildings of HVAC equipment is usually intermittent operation, its running time should be less downtime after the actual run-time. In the calculation of different regions and different times, different times of the various energy prices may vary. As a result of factors and uncertainties more, how to accurately calculate building HVAC equipment as a whole the actual energy consumption and operating costs, there is still a not completely solve technical challenges. Operating costs in addition to the energy consumption costs such as electricity, gas, coal, gas costs, they should also include arcConsumption of water, labor, etc.

In comparison, avoid economical map easy can be directly used for manufacturers of comparative data and results. I have found that electric heating of operating costs, three different equipment (electric boiler, water source heat pump and gas-fired heating boiler house) manufacturer's calculations. Through its detailed reconciliation of the calculation, discover different equipment manufacturers due consideration in the calculation of different angles, there are beneficial to your own product, is not conducive to the errors of others ' products or assumptions. The designer should give enough attention to, the data provided by the manufacturers should be careful analysis and verification.

Economic comparison of the design should be considered for investment, operating costs and equipment service life, in the same cycleas the basis for the calculation of the overall economy, and not simply a quote based on the device. For both heating and air conditioning requirements, consideration should be given to winter and summer equipment utilization issues comprehensive economic comparison of winter and summer. For domestic hot water can be cum for projects, should be considered domestic hot water supply of investment and consumption.

3. regulatory and operational issues

HVAC system capacity is usually the most throughout the year by close to unfavourable meteorological conditions, the system should have better performance in order to adapt to changes in load throughout the year. Adjust the performance of system programs, such as the use of VAV system and VRV inverter air conditioner system, an investment normally higher but less energy consumption, in economic terms and should be considered when comparing these factors. For some time use of office buildings, office buildings and teaching building, the design should be able to adapt to its night-time is not working in regulatory requirements.

Design management operation convenience is very concerned about the user. Air conditioning system automation level, you can reduce the number of managers and intensity, resulting in reduced labor costs, but make an investment, the operator's quality requirements. Air conditioning system is the use of automatic control, according to the actual circumstances and requirements, technical and economical comparison to determine. For large air conditioning systems and need regular adjustment and control of devices more engineering, automatic control, should be adopted to reduce the operational management of the workload. But the automatic control system should be simplified in order to improve system efficiency and reliability. For only only seasonal transition operations would not be appropriate for the use of automatic control valves. For some sections not simultaneously use of buildings or parts of a rented to the different units, the system sets the commercial buildings should take into account the respective management control and operating costs are paid statistics.

4. security issues

Design of security is ever consider fewer problems, with the United States "9 · 11" and other terrorist attacks as well as the emergence of SARS and the rapid spread of HVAC system security issues have become the focus of public attention, the SARS epidemic era, people seriously and even fear in the air conditioning system and not afraid to use, this will be on the HVAC industry have a profound impact. After careful analysis of these events, research and reflection, engineering design, equipment, operation management, regulatory and technical measures, and many other aspects to improve the security of your HVAC system. In large and medium-sized construction design phase, on the HVAC system for safety assessment will be necessary.

HVAC system security including flammable and explosive environment safety, fire safety, people, environment, security of important equipment goods environment security, system equipment safety five issues. In the design of the munitions factory and warehouse, coal mines and other explosive engineering ventilation and air-conditioning system, security becomes an important factor must be taken into account, should take appropriate measures for explosion protection technology programmes and. In the design of fuel gas boiler room should be considered flammable gases, liquids, disclosure of security problems, you should set the combustible gas leak alarm system and emergency ventilation system and mutual interlocking. Fire safety issues should be dealt with in accordance with the relevant fire design specifications to consider, as detailed here. Device security issues including refrigeration system security, North anti-freezing HVAC system, air-conditioning system, electric heating and fan interlock protection issues. When the programme design, consideration should be given to the HVAC system failure may on indoor important equipment and materials produces a negative impact, for example, important engine room, important repositories and heritage Treasury should not be used to set the ceiling fan-coil air conditioners, because once the chilled water system leakage would cause serious losses.

Personnel environment security principal includes HVAC system on human hazards and prevent terrorist attacks and prevent the spread of infectious diseases by these three aspects. Using ammonia refrigeration programmes, consideration should be given to ammonia leaks harm to the human body. Boiler room layout staff security issues should be considered. In terms of preventing terrorist attacks and prevent the spread of infectious diseases, you should be aware of the new air conditioning is the weakest link, so you must take the reliable precautions, the new outlet should be set in difficult to access, are not vulnerable to pollution. As the air conditioning system back into the air a lot, so it is most vulnerable to terrorists and biochemical attack air conditioning system, if you do not take special measures, it is also the most easily spread of epidemic diseases in the form of air conditioning systems. From this point of view, split air conditioner, multi-split air conditioner, fan-coil air conditioning system security better. In systems with the new amount of wind, in addition to some of the factors considered in the past, but also during the epidemic disease outbreaks, diluted concentration of indoor harmful viruses. In this regard, you should be careful not to go the other extreme, excessive air conditioning system security alarm is unnecessary. For example, in order to prevent the spread of infectious diseases and the use of the new wind of DC system, it is clearly unreasonable, this will make the investment, energy consumption and operating costs increased significantly, the key is to rationally determine system solutions and the new amount of wind, strengthening organized exhaust and insulation-heat recovery equipment, enhancing air filtration and disinfection. System of ventilation rate should be adjusted, usually run as normal air, during an outbreak of epidemic disease or indoor pollution by biochemical demandLarge air volume. Ceiling concealed fan coil air duct connections should be used, the ceiling should not be used as a static pressure Chamber of ceiling return air. Also in table coolers, cooling towers, evaporator and condensation water, where the reproduction of bacteria to take reliable sewerage and disinfection measures.

5. environmental impacts

With the rapid development of industrial production and the people's standard of living, environmental protection issues are becoming more and more attention, but the smoke-fired boilers and the northern city of the main sources of atmospheric, Beijing and other major cities on coal-fired boiler is severely restricted, and the limits of the area continues to expand. In these areas, the relationship between environmental impact as to the feasibility and design. Select the design should pay special attention to environment protection requirements increasing trend, avoid building built soon to be transformed. When the air conditioning equipment selection, paying special attention to the variety of freon refrigerant substitution process requirements, you cannot choose to have or will soon be disabled refrigerant for air conditioning refrigerant products. In this regard HVAC designers should have a sense of responsibility for environmental protection, while also considering building parties and users of affordability, not rashly, so as not to give the construction party and user added unnecessary burden. In the design of programmes and economic analysis, it should also be considering HVAC equipment for waste gas, waste water, waste and noise and pollution. How to design the emission of ozone layer destruction and damage caused by the greenhouse effect, systems and equipment throughout the entire process (including equipment, usage weeding out process of the whole process) of energy and resource consumption, a comprehensive, science, and quantitative assessment of the economy, is an in-depth study of the problem.

6. design of some mistakes in comparison

Because design is an influencing factor, professional highly technical work on complex technology, even the HVAC professional designers, to the many design options, selected the best solution is not easy for an outsider is the fog, look at the flowers. At present the work in some of the misconceptions. For example, consider using the latest technology design is best design, regardless of the use conditions and the blind pursuit of new technology trends, even as a selling point for speculation. In fact each programme has its applicability and scope, in its application, the advanced technology program might have become unreasonable or impracticable. A design plan for a project may be the best solution, but for another project may not be feasible, so select the programmes to be fashionable, when you cannot get this treatment. Also tend to believe that investment minimum programme is the best solution, but an investment programme may be low because of its high operating costs or equipment life is very short, needs regular replacement, in the long run is not economically viable. In the evaluation design, often considered a complex programme is a high level of scenarios. But in fact because of the more complex the system, the more often the equipment, the higher the investment, system's reliability, operability, controllability and serviceability, the greater the difference, so complex programmes does not necessarily have to be a high level of design, to meet the requirements of the system simpler, the better. In addition, when you do not choose a design without analysis of use of construction party, because building normally not HVAC professional designers, it is not possible to design a comprehensive technical and economic analysis. Therefore deal with the construction of the parties to enter into serious analysis, economic analysis, through comprehensive technical comparison to determine the best design.

7. closing remarks

HVAC design choice is a direct relationship to the HVAC project success and economic benefits and disadvantages of important issues. HVAC design and optimization is a broad, influencing factors more complex technology. An excellent programme of HVAC project design, design for a variety of factors involved in the overall consideration, making it the most comprehensive benefits. Comprehensive consideration of the factors, the more often the higher the level of programme design, and its design, the greater the workload and complexity. But since the current engineering design cycle generally shorter, HVAC professional design charge is too low, design fees and design of economic profit not hook and some technical problems are not solved and other reasons, in the actual design work are often not able to design more comprehensive programme more parameters: a comparative analysis and optimization, design choices prone one-sidedness and subjectivity, the resulting economic losses were considerable. It attracts attention of the technology of design management and two ways to make a lot of work. Comparison of the design must be selected on the design of the project's actual demand, environmental conditions, features, requirements, and the trend of environmental conditions, in-depth research on the characteristics of the various technical programmes, the applicable conditions and scope of the objective, in-depth analysis, HVAC technology development and trends have proven especially must be on a variety of designs on the feasibility, reliability, security, investment, energy consumption and operating costs, regulatory, operational, management convenience, environmental impact, comfort and appearance, and other technical and economic evaluation factors for objective, accurate and comprehensive analysis. The only way to various design options for comparison and selection of science, avoid one-sided and subjectivity of mistakes and economic loss.