2016 ASHRAE Winter Conference

Some HVAC engineers and designers are uncertain of the requirements for fire dampers and smoke dampers, especially with regard to the difference between partition types, because those requirements are typically found in the model building codes rather than the model mechanical codes. Some play it safe and specify fire and smoke dampers where they really are not necessary. This conference paper presents a fire and smoke damper summary for HVAC engineers and designers based on the model building codes. Topics addressed include the differences between fire walls, fire barriers, shaft enclosures, and fire partitions and between a smoke barrier and smoke partition, so that one can properly apply (or not apply) fire and smoke dampers where they are required and only where required. Eight helpful design tips are included. This paper is intended as a good introduction to the topic for less experienced engineers or designers; and a good review for the more experienced.

The use of trend data from Building Energy Management Systems (BEMS) is a cost-effective solution to provide the necessary data for the ongoing commissioning. This paper presents the use of trend data, recorded every 15 minutes, with a virtual air flow meter for the estimation of the outdoor air flow rate brought in the air-handling units. A virtual flow meter estimates the value of a physical variable in the heating, ventilating and air-conditioning system where a physical sensor does not exist. For this purpose, a mathematical model is used along with measurements from available sensors in the system. In this study, a virtual air flow meter was developed to estimate the outdoor air intake, and the results were presented as the ratio α of the outdoor air flow rate to the supply air flow rate.

Buildings are maintained at slightly positive pressure by the air handling units to avoid infiltration of unconditioned air. The conventional AHUs rely either on direct building pressure control or volume tracking control with a single loop proportional integral derivative controller to maintain positive building pressure. Even though this type of control structure is simplistic, the performance is usually not satisfactory. The purpose of this paper is to evaluate the performance of the cascade control on the building static pressure in comparison with the two conventional controls by simulation. An airflow model of an AHU system with PID controllers is developed. Performance of the two conventional controls as well as cascade control is simulated and subjected to wind effect, pressure fluctuations and flow sensor error.  The simulations conclude that the cascade control method stabilizes the control signal and compensates the error in flow measurement.

Wind driven roof ventilators have been in existence for over 3 decades. Developed in the USA, where it is primarily used as an attic /domestic ventilator, the roof ventilators have found a more industrial application in India considering the higher throat dia and material of construction. Evaporative cooling systems can be used for cooling at a fraction of the cost of conventional air conditioning systems. If used in a correct manner its ideal for sustainable and energy efficient comfort as well as process conditioning requirements. The ECS used for the case studies in this paper are systems that deliver higher air volume with lower energy consumption. Fabric Air Dispersion Systems were used for their lower carbon footprint and the fact that they can be removed and cleaned. Combining a precise ECS with WRV and using fabric ducts for delivery, an energy efficient system can be designed with perfect air balancing, optimum airflow patterns and utmost effectiveness to provide the necessary conditions in all parts of the building.

Advancements in computer technologies have made it economical for HVAC equipment manufacturers to implement computational fluid dynamics (CFD) in order to aid in the design process. The benefits of using CFD analysis include reducing the amount of time to optimize a given design, ease of identifying potential failure points in existing products, and reducing the number of laboratory experiments required. CFD offers the ability to visually characterize the airflow and heat transfer through an AHU and assess uniformity as it enters the heat exchanger. This paper presents the CFD models used to characterize the airflow uniformity in order to increase the overall heat exchanger efficiency in an AHU.