This paper examines the energy flow in buildings and the complexities of HVAC system design, highlighting important factors for effective and efficient thermal management [1] [2] . Energy flow, both positive and negative, comes from different places in a structure. Air temperature is determined by sensible heat, but humidity levels are affected by latent heat that comes from structures such as windows, roofs, and walls [3] . When ventilation or infiltration is combined with a temperature difference between the interior and outside air, heating or cooling must be provided; these losses or gains might be considered sensible or latent. Moreover, this complex energy interaction is facilitated by internal heat sources including equipment, people, and illumination. In the end, the HVAC system’s heating or cooling load is determined by the total of these various energy flows.

Determining design loads often involves streamlining assumptions and modifying techniques to accommodate certain building kinds. For minor building heating loads, for example, steady-state techniques are sufficient; nevertheless, rapid fluctuations in sensible and latent loads are critical for air conditioning system size. A crucial component, meantime, is the methodical use of engineering concepts in duct design. In order to enhance HVAC system efficiency and ensure exact delivery of conditioned air to different zones, it looks for the best route for conditioned air, taking into account air velocity, pressure drops, and temperature properties [4] .

Important duct design elements include pressure drop studies, friction loss computations, and using psychometrics to comprehend the thermodynamic characteristics of air. By following these guidelines, engineers can regulate temperature and humidity, maximize airflow dispersion, and improve indoor air quality [5] . The equal friction method, which is popular for commercial HVAC systems because it is easy to use and efficient for medium-scale to large-scale installations, will be the main topic of this paper [6] .

Maximum of 250 patrons (about 60 tables).

Cooking staff-6.

Waitpersons-10.

Hostess-1.

120 × 80 ft rectangular foundation, concrete slab-on-grade surface covered with indoor/outdoor carpeting.

The building sketches have been done in Revit. It is a powerful Building Information Modeling (BIM) software that allows engineers and designers to create a comprehensive digital representation of the building’s MEP.

The building area details in square feet are as follows ( Table 1 ).

Revit Software has been used to generate the Architectural drawing of the building as shown in the following photos [7] ( Figure 1 and Figure 2 ).

Weather information that is used in design for locations in the USA and throughout much of the world is available in the ASHRAE Handbook, Chapter 14, “Climatic Design Information” (2009). Table A1 (English units) (see Appendix) is abstracted from this database and gives some of the basic design weather information for four USA locations.

For this project, the chosen design location is Madison, WI, with the following weather conditions:

Summer: 90˚F db, 73.7˚F 𝑤𝑏.

Winter: −10.3˚F.

As shown in Figure A1 (see Appendix), the recommended temperature ranges are between about 67˚F and 76˚F (20˚C and 25˚C) for winter and between 74˚F and 82˚F (24˚C and 28˚C) for summer. The humidity range is less precise, and ranges from about 20% to 80% RH. The upper humidity limit of 80% reflects that people are uncomfortable when their skin feels damp, although an upper limit of 60% may be a better comfort level. The lower limit, corresponding to a humidity ratio of 0.044 lbm/lbm, is a level that dries out skin and makes one feel uncomfortable. The middle of the winter comfort range is 72˚F and 50% RH, and in summer is 77˚F (25˚C) and 50% RH. The conditions at the middle of the comfort range are often used in design calculations.

Therefore, the required interior design conditions are:

Summer: 77˚F and 50% RH.

Winter: 72˚F and 50% RH.

The amount of heat a person gives off depends on how active they are. ASHRAE has a table in their Fundamentals guide that lists these heat values for both sensible ( Table 5 ) and latent heat gains based on activity. You can calculate the total heat load from people by using these values, the number of people, and a cooling load factor, as shown in the equation below:

$Qc=N\times \text{SHG}\times \text{CLF}$ (4)

Formula 4 [11]

Where:

N = Number of People.

SHG = Sensible Heat Gain, Activity dependent.

CLF = Cooling Load Factor.

The cooling load factor takes into account the time lag factor and if it is not given it should be assumed to be 1.0. Using the data obtained from ASHRAE on Heat gain ( Table A4 ), the following loads are obtained:

The total cooling loads for each zone are sum of the latent and Sensible heat loads calculated above ( Table 6 ).

Based on the minimum recommended outdoor air flow rates in Table A3 , the design outdoor airflow to provide necessary ventilation for each zone ( Table 7 ).

Zone pressures play a crucial role in maintaining a balanced and efficient HVAC system. During the design, consider the desired pressure differentials between zones based on the intended use of each space [17] . Proper design ensures that the HVAC system effectively meets the specific needs of the building [18] .

To determine the pressure in each zone, establish the total pressure of the supply fan based on the longest duct run:

$L_{\text{longest}}=9+6+4+3+15+32+49=118ft$

The pressure at the exit of the AHU is then determined by adding the pressure drops along this run:

$\text{PAHU}=14.69+7.97+3.74+0.75+1+1.49+6.98=36.62Pa$

The pressures in each zone can be based on this pressure and obtained ( Table 12 ).

The process of designing a restaurant’s heating and cooling system requires striking a careful balance between selecting components that are both economical and efficient and satisfying capacity demands for a range of situations. Keeping both initial prices and ongoing expenses in mind, the objective is to guarantee a cozy and healthful interior atmosphere [19] . A key factor in achieving balanced pressure drops and optimal energy efficiency in HVAC duct design is the equal friction approach, which is well-known for its effectiveness. It emphasizes the need for constant friction rates throughout the ductwork. In order to obtain the required friction rate, which promotes equal airflow distribution and system balance, engineers use a methodical procedure that takes into account aspects including total airflow needs, zoning, and iterative modifications to duct diameters. In order to maintain maximum performance, it is imperative to consider space limits, equipment compatibility, and constant system monitoring. This technique complies with industry requirements, guaranteeing reliability in the field. All things considered, the equal friction approach is a useful tool for creating HVAC duct systems for restaurants that are both balanced and effective.

● Find design day weather conditions.