Total hydronic balancing a handbook for design and troubleshooting of hydronic hvac systems
Uiterlijk 24 januari in huis
Increasing awareness of how important the indoor climate is to human well-being and productivity has encouraged manufacturers to develop sophisticated control technology. But many heating and air conditioning plants do not provide the desired indoor climate at a reasonable energy cost. How ís “this possible? Controls are certainly not to be blamed. Most controllers will do exactly what their manufacturers claimbut only if permitted to do so. The fact ís that many controllers are being prevented from doing their job, usually by one or more of the following factors:
1 Interference between circuits e Flow incompatibility at interfaces e Incompatible hydronic and control designs
2 Uneven flow distribution
Any of these can incapacitate the controllers, no matter how advanced they are.
Total Hydronic Balancing is a method of integrating control loops into a hydronic system in order to obtain the desired indoor climate at minimum operating cost.
Mr. Robert Petitjean is the Director of” Technical Systems at Tour & Andersson.
He has given well over 300 seminars on hydronic systems design, attended by . more than 14 000 HVAC practitioners in [7 countries.
Mr. Robert Petitjean is also a lecturer in control theory at the “Université du Travail” of Charleroi, Belgium, Section of Industrial Erigineering.
Working in a consulting engineering practice, with a research and development brief, involves me in the technological aspects of projects and their installation, management and operational problems. What is abundantly clear, from my experience, is that excellence in design and construction is the result of well motivated team members who have had the best possible training in the complex disciplines and activities of the construction industry.
This industry and, in particular, the building services engineering sector, must be able to see its way ahead in terms of education, technology and research for the international construction market of the next century.
Engineering is the application of science, and engineers use available technology and extensions of traditional theory to satisfy the needs of the client at any given point of time. Truly new ideas and solutions are rare, but innovation, development and technology are always necessary for progress and improved solutions.
The availability of techniques and technologies is crucial to the solutions provided by engineers to overcome problems and satisfy client needs. It is essential, therefore, that manufacturers provide good technical and performance data for three classes of user: the design engineer, the contracting engineer and the end user. Only then will total quality management be possible.
It is therefore very welcome to find a book which addresses this need, written by an academic who is also directly involved with manufacturing industry. Total Hydronic Balancing provides comprehensive coverage of this fascinating technical field, which can be used as an advanced tool and textbook. It will be useful from the classroom through to operational practice in occupied buildings.
The volume is entirely devoted to the design and application of water systems for balancing, confirming that in hydronic systems, the important concept is to recognize circuit interactivity and the advantages of designing control loops together and not separately.
Education is of fundamental importance to produce suitably trained incorporated and technician engineers together with skilled craftsmen, all of whom are so vital for our future. Without suitable academics at all levels we cannot train wholly effective graduates and technicians, and without quality engineering students we surely cannot sustain our technological needs into the 21st century.
Robert Petitjean demonstrates that education, from the classroom onwards, is an amalgam of good teaching allied to comprehensive theoretical and practical training aids. This volume contains the relevant information to teach, design and operate the systems which are so essential for our future comfort, in a manner sensitive to sustaining our precious natural resources.
CONCERNING COMFORT
The essential objective in the design of any heating and air conditioning plant is to obtain a comfortable indoor climate, minimising costs and operating problems.
We have become aware of the importance of the indoor climate on human wellbeing and productivity. This has led to more severe requirements, encouraging manufacturers to develop new sophisticated controllers, including optimization functions, advanced control and supervision equipment.
In theory, these new technologies appear adequate to satisfy the most demanding requirements and to provide opportunities for increasing comfort while making substantial energy savings.
In practice however, even the most sophisticated controllers cannot always achieve their theoretical performances. ‘Fhe reason for this is simple: the ideal conditions that normally must be satisfied for their correct operation are not respected. The consequences on comfort are not negligible.
If we systematically analyse the behaviour of HVAC plants, the following problems are often observed:
DJ The required room temperature is not achieved in all rooms, especially after a high load variation.
OD When the required room temperature can be obtained, it continuously oscillates despite the use of sophisticated controllers on terminal units. These oscillations usually appear at low and medium loads.
D Although production units have sufficient capacity, it cannot be transmitted at high loads and particularly in start up phases.
Users also complain about annoying noises generated by the installation. In air conditioning, large variattons in the supply air temperature are often difficult to support. In hot countries there are sometimes cold and annoying drafts inside rooms that make seme people talk about summer outside and winter inside. Discomfort created by these plants is sometimes seen as an incurable disease, as if we could not hope for better. The worst is that this discomfort is expensive. This type of plant can consume 40% more energy than HVAC plants that are operating satisfactorily.
These malfunctions cannot be corrected by an even more efficient control system. They are often due to design faults in the hydronic circuit itself.
Energy is transported through the installation normally by hot or cold water. Controllers cannot efficiently control an installation which is initially suffering from circulation problems. Local controllers cannot compensate for a lack of flow in some zones in which design conditions are impossible to reach since the control valves cannot do more than open fully. A central controller cannot control a nonhomogeneous plant. In heating, there is no common relation between the hot water temperature and the outside conditions, applicable to a non-balanced plant, a different relation is necessary for every room.
Water flows must therefore be distributed correctly throughout the plant.
This fact is obvious, but itis not always given the attention that it deserves. Even if the plant is well designed, two terminal units with different capacities, connected to a common pipe, demand different flows. This can only be obtained by local flow adjustments. Furthermore, assuming that all preliminary settings were calculated by computer, they still have to be put into practice. Moreover, last minute changes to the plant during construction can invalidate calculations carried out, with a dramatic effect on the actual flow distribution.
We are sometimes surprised to find that the installed power is not transmitted to the distribution circuit. This aspect of the problem may become pernicious as it only occurs at some moments. Under these conditions, control becomes difficult or even impossible for adaptive controllers, for example. This type of problem may occur in plants equipped with the most recent control technology, since the problem is generally due to hydronic unbalance in the plant.
Both the importance and complexity of hydronic balancing are often underestimated. The result is that plants in which the hydronic balance has been satisfactorily solved are still in the minority. This surprising observation could be explained in the past by the fact that inexpensive energy did not motivate persons responsible to concern themselves with such an elementary and apparently uninteresting problem as balancing.
However, increasing comfort and energy performance demands impose severe constraint. The desire to achieve these objectives with oversized plants remains a dream, since this oversizing simply creates more problems.
In order to create substantial energy savings and at the same time improving the comfort, balancing must be approached globally. Production and distribution, and control loops, must be balanced in order to ensure plant homogeneity and compatibility of flows at interfaces.
These questions are considered in the Total Hydronic Balance investigation field.
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Taal: en
Bindwijze: Hardcover
Aantal pagina's: 485
Kaarten inbegrepen: Nee
Illustraties: Met illustraties
Hoofdauteur: Robert Petitjean
Dyslexievriendelijk: Nee
Extra groot lettertype: Nee
Product breedte: 180 mm
Product hoogte: 34 mm
Product lengte: 254 mm
Studieboek: Nee
Verpakkingsgewicht: 1388 g
eWaste: Nee
EAN: 9789163026263