This presentation will provide an overview of the Design Guide by highlighting the essence of all twelve chapters. Practitioners with a firm understanding of successful CHP applications will understand that successful CHP is first and foremost reliable economics.  This means that matching CHP electricity and thermal production with site loads is essential.  Targeting addressable thermal loads then become the primary focus of CHP design.  Finally, accounting for the right economic factors will result in a good CHP assessment.

The CHP Analysis Tool builds on an analysis engine used in assessing sites for CHP applicability during 10 years of work with the DOE and the private sector. The ASHRAE CHP Analysis Tool has been further developed as part of ASHRAE research project RP-1592 to provide an initial understanding of the CHP potential for a given site. The CHP Analysis Tool provides a consistent and tested means for assessing CHP system economic performance for building with weather dependent and process loads using monthly utility billing data.  The results of the analysis are intended to be used for guidance purposes only.

One of the primary noise transmission paths in buildings is from HVAC equipment through ventilation ducts. The ASHRAE Handbook provides tables for estimating the attenuation of lined and unlined ducts up to 10 ft (3.05 m) in length. The aim of this research is to suggest and validate a finite element approach to determine the attenuation of ducts of any length and dimension. The approach detailed simulates the standard measurement approaches for assessing duct attenuation. The duct air space, including the source and termination, is modeled using acoustic finite elements. Poroelastic finite elements are used to simulate the fiber lining, and the metal ductwork is modeled using structural finite elements. The model is used to determine the insertion and transmission loss of unlined and lined ducts. Predicted results are compared to measurement with good agreement.

The primary path of noise propagation in buildings is airborne transmission from building equipment through ducts. Attenuation is increased if elbows or side branches are introduced into a duct. In a companion paper, finite element analysis was used to predict the insertion loss of straight lined and unlined ducts and results were validated with measurement. In this work, finite element analysis is used to predict the attenuation of elbows and side branches. Results for elbows and branches are compared to the ASHRAE Handbook with good agreement. In addition, an important secondary noise transmission path is through duct walls into rooms. This path, which is often termed breakout noise, is also investigated using the finite element approach and results are correlated with an analytical solution and the ASHRAE Handbook with good agreement. Of note, it is demonstrated that the breakout transmission loss is much less than the insertion loss through lined rectangular ducts at some frequencies. This suggests that breakout noise may be the dominant noise path at some frequencies.

This paper summarizes an experiment campaign on alternative refrigerant evaluation for R-22 and R-410A mini-split systems. The experimental evaluation was performed according to ANSI/ASHRAE Standard 37 and the performance was rated according to ANSI/AHRI 210-240 standard. The paper presents the relative performance (efficiency and capacity) of the alternative refrigerant compared to the baseline refrigerant at the different operating conditions. The paper ends with concluding remarks about the alternative refrigerants for R-22 and R-410A applications in high ambient temperature regions.

In this paper, the oil retention in a microchannel type evaporator was measured and its effects on heat transfer and pressure drop characteristics are presented. The microchannel heat exchanger was a single pass, aluminum louvered-fin type evaporator with multi-port microchannel tubes installed vertically.

Flammability testing studies were conducted to support a methodology to optimize GWP to flammability for blends of R32, R1234yf and R125. Performance modeling studies were conducted to guide the best design of experiments for the flammability testing that optimize performance. Minimum ignition energy and burning velocity characteristics were determined for various blends of R32, R1234yf and R125 to determine flammability characteristics. This paper will discuss the results of these studies.

Global pressure to control climate change is driving the development of new regulatory policies that restrict and/or lower the direct GWP impact of fluorocarbons (or F-gases). These demands have resulted in researching a whole new class of fluorocarbons called unsaturated fluorocarbons or commonly referred to as hydrofluoroolefins (HFOs).  This paper provides an overall assessment of the application of the new HFO refrigerant R-1233zd(E) in stationary HVAC chillers. The presentation also reviews thermodynamic cycle performance and heat transfer characteristics relative to R-123, R-245fa and R-134a in a centrifugal chiller application.

Regulatory and voluntary actions are beginning to limit the direct global warming potential (GWP) of refrigerants used in many applications. A new class of fluids called unsaturated hydrofluorocarbons or hydrofluoroolefins has been developed to address this concern. These new fluids are being blended with existing HFCs to obtain lower GWP replacements or substitutes for today’s refrigerants. This paper provides an overall assessment of the application of R513A, an azeotropic blend of R1234yf and R134a (56%wt/44%wt), as an alternative to R134a. R513A provides specific environmental and safety features of interest including: no impact to stratospheric ozone, 56% reduction in GWP compared to R134a, no significant secondary adverse environmental impacts, low toxicity and non-flammability. This paper reviews the thermodynamic cycle performance and heat transfer characteristics of R513A relative to R134a.

Ambient particulate matter (PM) air pollution is critical to human health and well-being given the association of urban air pollution with increased respiratory and cardiovascular mortality. For urban office buildings in big cities, use of economizers has dramatically increased recently for energy saving and ventilation purposes. The objective of this paper is to examine outdoor-indoor transports of ozone and PM_2.5 (particles < 2.5 micron in diameter) for urban office buildings considering economizer operating modes. This study employs multi-zone contaminant transport model for prediction of outdoor-indoor pollutant dynamics in two cities: Los Angeles and Beijing. The model simulates an infiltration of ambient ozone, PM2.5 (< 2.5 micron), into a DOE reference building (medium office) based on outdoor climate condition, outdoor intake and filtration efficiency. Seasonal variations are also considered to capture the influences of high ozone levels during the summer in LA and elevated particle concentrations during the spring season in Beijing.

Exposure to ambient fine particles (PM_2.5: particles < 2.5 μm in diameter) and ultrafine particles (UFPs: particles < 100 nm in diameter) has adverse effects on human health. Residential buildings greatly impact human exposure to outdoor particles because people spend more than 90% of their time indoors (and much of that time at home) and outdoor particles can infiltrate through building envelopes and mechanical ventilation systems with varying efficiencies. This paper will model the impact of various combinations of central forced air HVAC filtration and mechanical ventilation systems on indoor concentrations of fine and ultrafine particles of outdoor origin in three types of residential buildings (i.e., older, existing and new homes).

Exposure to airborne particulate matter is connected with adverse human health effects. The majority of human exposure to airborne particles occurs inside buildings. In order to improve indoor air quality by reducing indoor particle concentrations, high efficiency particle filters installed in central forced air heating, ventilating and air-conditioning (HVAC) systems are being used. ASHRAE Standard 52.2 relies on a method of laboratory testing to measure the performance of general ventilation air-cleaning devices to assist end-users in their selection of appropriate air filtration products to increase living or working environmental quality. In this project, an in-situ test method is used to measure the particle removal efficiency of a wide range of commercially available filters in 28 particle size ranges from 0.01-10 µm in diameter.

Membrane-based energy recovery ventilators (ERV) are an effective means of reducing energy cost and allow for scaling down HVAC equipment. Owing to their compact geometry and rough surfaces of the porous membrane substrate, ERV exchanger cores can be fouled by airborne particulate matter. In this study, the influence of particulate fouling on the membrane-based ERVs was investigated via accelerated material- and core-level fouling experiments.  The core-level experiments, inside an aerosol wind tunnel (AWT), investigated the effect of dust accumulation on the performance of cross-flow cores (including sensible and latent effectiveness, and pressure drop) through comparing pre- and post-fouling performance tests of two core samples. The influence of the membrane surface exposed to particle-laden air, and working airflow rates were considered during AWT tests.

This presentation will focus on the high level need for HVAC equipment, particularly VRF systems,  to participate in activities like demand response and help the grid operators manage the increasingly complex integrated grid.  With numerous new energy sources coming online at a rapid pace, like solar and wind, managing the elctric grid has become a significant challenge.  This presentation will set the stage for the remaning three presenters by elaborating on challenges.

Southern California Edision (SCE) has many HVAC demand response programs. VRF systems offer interesting alternatives that traditional HVAC systems cannot offer.  This presentation focuses on the potential based on conditions in California mainly from a program standpoint considering installed tonnage and various services offered by the VRF systems.  An aggregated approach , i.e. collecting all VRF systems together as a single load will also be discussed.

Variable refrigerant flow (VRF) systems are primarily associated with energy efficiency (EE) and superior customer comfort. The higher energy efficiency is achieved by utilizing variable speed compressors, modulating fans, electronic expansion valves and multitude of refrigerant management features. VRF systems, with their modulating components, onboard instrumentation and communications capabilities, are great candidates for implementing both EE and DR at the same time. This talk highlights the features of one of the manufacturers technical capabilities and how the existing features can be utilized to provide unparallel customer comfort as well as grid services to further improve reliability of our electrical grid.

Variable refrigerant flow systems are perfect candidates for providing energy efficiency and demand response at the same time.  This talk will elaborate on some existing DR enabled installations around the world including the US. Data gathered from various sites will be used to showcase the capabilities of the VRF systems for providing DR.

The energy use-related effects of ultraviolet germicidal irradiation (UVGI) to mitigate biological fouling (biofouling) of a chilled water cooling coil are investigated via a field study. A visibly bio-fouled cooling coil in an air-handling unit serving an operational building in a hot, humid climate is monitored for 5 months to establish a fouled coil baseline. Parameters monitored include air flow rate, airside pressure drop, air temperature and humidity upstream and downstream of the coil, chilled water flow rate, entering and leaving chilled water temperature and waterside pressure drop. A UVGI coil irradiation system is installed on the downstream side of the coil following typical manufacturer guidelines, and the system is then passively monitored over a period of 10 months. An average improvement of 5.2% to 7.9% in coil airside pressure drop, and 11.9% to 12.7% in heat transfer coefficient (both 95% confidence interval) are estimated by comparing data from the baseline and post-irradiation periods. Complexities of the physical phenomena involved, e.g. the effect of both airflow and latent load on airside pressure drop, are taken into account.

The goal of this project was to assess the potential benefits of using a highly-controlled surface wettability to preferentially condense (and therefore locate) water droplets on a heat transfer surface during the early stages of frost growth to affect the thermophysical properties of the frost layer (i.e. density, thermal conductivity, etc.). It was postulated that a thinner, denser frost layer might lead to improved heat conduction (and therefore improved air-side heat tranfer) and longer operational periods before defrosting becomes necessary. The retention of less water on the heat transfer surface following defrosting might also be used to slow frost growth in the subsequent cycle and therefore lengthen the operational cycle. Thus, accompanying this objective was the goal of creating heat transfer surfaces that more completely drain the melted frost layer during an applied defrost cycle.

It has been noticed by many users that whenever a germicidal UV disinfection is performed in a room, there is often a strange odor left behind. It is not ozone, which can be easily identified and measured. It is more like a slightly pungent smell. It's actually easier to acknowledge the smell than to describe it. Until now, no satisfactory scientific explanation about the origin of this peculiar odor has been provided. In this paper, the authors provide a clear explanation of the source of this odor. Evidences show that the root cause seems to be the interaction of UV with airborne dust.

An overview of what makes modern absorbers different from absorbers in the past. How these differences result in a wider suitable application range to solve problems and provide solutions to the HVAC and CCHP marketplace.  A recent project for a retail big box store will be covered that does a good job of highlighting these changes and how the store's HVAC, domestic hot water and “sub-cooling” of the low temperature refrigeration is accomplished by the absorbers in a fully integrated CCHP system.  This store can also operate with or without the local electric grid.

This presentation on absorption heat pumps (Lithium Bromide-Water) explains the working principle and an overview of the cycle, classification or types, energy balance,  construction/illustration of the equipment, technology benefits and constraints, coefficient of performance, crystallization, lift, applications and application considerations.

The required length of vertical ground heat exchangers (GHX) used in ground-coupled heat pump (GCHP) systems is determined to make the outlet temperature from the GHX remains within certain limits at peak ground load conditions. These conditions may not necessarily occur after 10 or 20 years of operation and often occur during the first year of operation. The primary objective of this paper is to develop a general methodology, using the framework of the ASHRAE bore field sizing method, for the calculation of the total required bore field length on a monthly basis during the first year of operation.

District cooling plants using large electric powered water-cooled vapor compression machines in warm weather regions are gaining popularity. Providing an economic mass scale cooling for buildings. This paper proposes to replace such a system with the use of direct-fired two-stage absorption chillers located at the power generation plant. Absorbers energized by the exhaust of a gas turbine power generation plant can be used to provide chilled water to cool nearby buildings. Calculations presented in this document can be used to analyze the feasibility of such an investment.

Liquid to air membrane energy exchangers (LAMEEs) are used to transfer heat and moisture between air and desiccant solution streams. LAMEEs use semi permeable membranes to prevent the transfer of desiccant droplets to the airstream, which guarantee high levels of indoor air quality. When a LAMEE is used for air cooling and dehumidifying, energy of phase change is released as the desiccant solution absorbs moisture from the humid airstream. Consequently, the temperature of the desiccant solution increases as it flows along the exchanger which decreases the LAMEE’s effectiveness. A 3-fluid LAMEE is a novel type of LAMEEs which includes a cooling water circuit to cool the desiccant solution along the exchanger. The main contribution of this paper is that it quantifies for the first time the amount of phase change energy released in liquid desiccant energy exchangers used for air cooling and dehumidifying process.

This paper investigates the possibility of using a Tesla turbine as an alternative air-conditioning compressor drive unit rather than the traditional method of linking the compressor rotor to the vehicle engine crank-shaft belt or chain. Interest in Tesla turbines has recently gained momentum due to the possibility in obtaining high efficiency in energy conversion, as claimed by the inventor Nikola Tesla. This paper investigates the possibility of driving the air-conditioning compressor using the hydraulic energy available in the engine lubrication oil piping provided by the engine oil pump. Tesla turbines are easy to adapt and can cover a range of flow rate capacities. Using such a system for energy conversion can lower capital equipment costs and improve the turbine life span. Contributing to sustainable engineering development.

The as-installed energy efficiency of unitary systems is much less than that of central systems, and the efficiency gap widens as systems age due to maintainability issues.  Energy engineers and service technicians use indirect indicators of equipment performance and make adjustments according to manufacturer guidelines and standard field practice, which varies with technicians’ level of experience.  Growing numbers of unitary systems combined with shrinking budgets result in deferred maintenance, and long-term operation of equipment at degraded levels. Energy efficiency is a metric that must be measured to be optimized.  This paper reports on field testing of continuous sensing of actual operating energy efficiency to control unitary equipment operating parameters, provide remote fault detection diagnostics and support maintainability. The energy efficiency of most unitary HVAC systems is much less than chilled water systems and limited cost-effective choices exist for increasing their energy efficiency.

In the U.S., there are 14.4 M electric-heated dwellings using 0.16 quad/year for heating in cold regions, e.g. ASHRAE climate regions IV and V. Conventional air-source heat pumps (ASHP) do not work well in such cold zones, due to high compressor discharge temperatures, large pressure ratios and inadequate heating capacities at low ambient temperatures. Consequently, noticeable portion of auxiliary strip heating has to be used to meet the building heating load. Two options of tandem compressors were studied, with one using two identical, single-speed compressors, and the other using two identical, vapor-injection compressors. The system modeling and laboratory testing results will be presented in the paper.

A 250 m², two story, residential home of the style typical of the Gaithersburg, Maryland area was constructed in 2012 to illustrate technologies employed to produce a netzero energy home. It functions as a laboratory to support the development and adoption of cost-effective NZE designs, technologies, construction methods, and building codes. The primary design goal was to meet the comfort and functional needs of the simulated occupants. The first annual test period began on July 1, 2013 and ended June 30, 2014. During this period the heating and air conditioning of the home was performed by a novel air-source heat pump that utilized a reheat heat exchanger to allow hot compressor discharge gas to reheat the supply air during a dedicated dehumidification mode.

The application of vapor injection to the compression process leads to a decrease in discharge temperature, extending the operating envelope to lower suction pressures. Additionally, it increases the coefficient of performance as well as the heating capacity under these conditions. Vapor injected compressors are therefore ideally suited for cold climate heat pump applications. This paper introduces a PI-type mapping of a dual port vapor injected compressor’s performance data trained with data from both, in-system testing as well as test-stand testing.  The in-system testing was conducted in a prototype cold climate heat pump, where injection mass flowrates and suction superheat were a result of the operating conditions.  In contrast, suction superheat of the test-stand data was fixed while injection flowrates were dictated by the test plan. These differences result in limitations of the mappings if the model is trained with only one of these sets.

Vapor injected compressors are one of the promising technologies for cold climate heat pumps because it enables compressor operation with a large range of evaporating temperatures at acceptable efficiency. However, the large operating range also makes it difficult to generate empirical maps that are applicable to most of its operating conditions. This paper discusses a method to create an empirical map using the Buckingham-PI theorem and estimates the resulting extrapolation uncertainty. Data from the laboratory testing of a cold climate heat pump were used to generate the map. The uncertainties from model random error and training data were calculated to examine if the model is reliable at extrapolation.

Brazing is a practical, fast and relatively low cost joining method.  Both aluminum and copper heat exchangers and many miscellaneous component connections are brazed.  In addition, field service repair often requires re-brazing that can take place under less-than-ideal conditions.  However, to achieve a reliable and leak-free braze joint, adequate surface preparation and proper control over heating parameters are required.  Unfortunately, if inadequate brazing techniques are used, thermal degradation at the interior surfaces of tubing can take place.  The degradation can lead to the formation of scale that may dislodge and cause contamination of bearings or valves in the HVAC&R system.

To guarantee long equipment life, the construction and assembly of heat exchangers, piping, valves and compressors requires metalworking fluids compatible with the refrigerant and lubricant without cleaning prior to final brazing or assembly. The movement of the industry to chemically unstable low GWP refrigerants and aluminum heat exchangers has necessitated the development of new metalworking lubricants and additive packages.  Continued interest in developing environmentally friendly materials with low VOC, no wax formation, and excellent compatibility when tested by ASHRAE Standards 86 and 97 continues to drive the manufacturing market to search for the next generation of sustainable metalworking fluids.

There is growing pressure on installation contractors to get refrigeration systems up and running with as little on-site work to keep projects within budget. Unfortunately, this trend can result in systems that meet the immediate need to keep the product cold but are not optimized to minimize life cycle operating costs, including energy usage and maintenance.  An installation plan that includes measures to correctly setup the refrigeration system can result in both significant energy savings as well as superior reliability.  This discussion will focus on several high priority areas that have historically proven to provide the most benefit.

More manufacturers are commercializing air conditioners and heat pumps using HFC32 refrigerant because of its environmental, energy efficiency and economic benefits. This presentation explains points to consider for installation and service practices when changing over from HCFC22 or R410A to HFC32. The presentation covers aspects such as the impact on tooling, refrigerant cylinders, working pressures, safety requirements as well as the impact on recovery and reuse. The information is intended for installers and service technicians but is also useful for training centers, associations and policymakers involved in training and certification schemes for people working on equipment containing a refrigerant circuit.

Output variability and low generating inertia associated with solar and wind electric power generation increase the requirement of grid-scale flexibility services, called ancillary services. Commercial buildings consume a significant portion of electricity in the United States and can help provide demand-side ancillary services through use of their HVAC systems.  In order to investigate the performance of a common commercial HVAC system while providing ancillary services, a dynamic model of a representative variable air volume system was developed.  The model has been used to simulate and evaluate the provision of spinning reserve and regulation ancillary services using common demand response strategies.

Fast fluid dynamics (FFD) is an intermediate model that can provide fast and informative building airflow simulations. To further increase the computing speed of FFD, this study proposed applying the coarse-grid projection (CGP) scheme in FFD, which solves the momentum equation on the fine grid level and the pressure equation on the coarse grid level. Through validating the CGP scheme with building airflows of varying complexities, this study found that it could significantly accelerate simulation speed of FFD while not causing negative impact on the simulation accuracy.

This presentation describes an evaluation of the cycle performance of thirty-nine refrigerants identified in the AHRI low global warming potential (GWP) Alternative Refrigerants Evaluation Program (Low-GWP AREP) in a typical air-conditioner.  A methodology was developed using weighting factors to rank the alternative refrigerants either emphasizing the importance of large COP or the importance of reduced system size.  The two ranking methodologies produced different rankings of the alternative refrigerants; however, the top three ranked refrigerants had at least two refrigerants in common with each other.

While the possible impact of refrigerant leaks and subsequent dispersion in an occupied space pertains to a wide variety of applications, dynamic models that accurately describe dispersion phenomena in the built environment have not been extensively explored in the literature. This paper builds on previous work by assessing the performance of well-mixed models via a comparison to computational fluid dynamics simulations and studying the behavior of refrigerant dispersion in multiple connected spaces. Results indicate that the well-mixed models are not able to capture variation in the geometric parameters very accurately, and should be used cautiously, while the studies of the dynamics in multiple spaces highlights the importance of the location of ventilation sources and sinks.

This paper investigates the performance of liquid overfeed and DX refrigeration systems and includes components performance and system balance. This project includes the design of two refrigeration circuits, liquid overfeed flooded and DX with a common condenser, and analyzes the performance of the heat exchangers and their impact on the overall circuit’s performance. Several design techniques and methods are considered, including geometry and construction of heat exchangers. The performance of the two circuits is compared for four operating temperatures: -20°C (-4°F), -10°C (14°F), 0°C (32°F) and 5°C (4°F) and analyzed to ascertain circuits operation. DX evaporators are often utilized operating at -10°C (14°F) and below for relatively small duty systems, below 25kW (7.1 TR). However, liquid overfeed flooded evaporators’ are rarely seen practically for systems in this range. The performance of the DX and liquid overfeed flooded evaporators’ is also analyzed for small duties at the four operating conditions.

The eighty-year-old single pressure absorption refrigeration system invented by Albert Einstein and Leo Szilard is attractive as it has no mechanical moving parts and can be driven by heat alone. The literature on the refrigeration system is scarce and only theoretical analyses are available. In this paper, adversities of the primitive design and the operation of the refrigerator prototype are discussed. The prototype is able to achieve temperatures between 8°C and 14°C. Five pairs of heat inputs between 53 W and 111 W are studied. Cooling capacities decrease (from 34 W to 15 W) when the generator heat input increases, but cooling capacities increase (from 17 W to 30 W) when the bubble pump heat input increases. The highest COP is 0.25 when the heat inputs to generator is 53 W and to bubble pump is 89 W. The ideal cooling capacity and COP are 40 W and 0.28, respectively.

This article reports the outcome of an experimental study on the evaluation of photocatalytic oxidation reactions of light alcoholic volatile organic compounds with nano TiO₂ catalysts at different indoor air conditions. The removal efficiencies of tested individual volatile organic compounds and their by-products were compared at three different parts per billion-level challenge concentrations. Acetaldehyde and formaldehyde were identified as primary by-products, and no significant catalyst deactivation was found during the experiment. The reaction pathways and the selectivity of the reactions were investigated at different relative humidity levels.

Volatile organic compounds (VOCs) are indoor air pollutants with many adverse health effects for humans. Ozone reactions with human surfaces are an important source of VOCs in aircraft cabins. This investigation developed empirical models for computing the emissions of several major VOCs from ozone reactions with human-worn clothing. The empirical models were used to compute the contributions of human surfaces to these VOCs in an aircraft cabin mockup under different environmental conditions after they were compared with the corresponding experimental data. The models can determine ozone-initiated VOC concentrations in the breathing zones of the passengers.

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.

Energy efficiency, heat recovery and cost efficiency of commercial refrigeration systems still have a large development potential for systems applying R744 as the only refrigerant. The system architecture has to be in the focus with respect to increase the system efficiency when these units are operated at elevated ambient temperatures. The objective of this work is to investigate the energy required for different R744 commercial refrigeration systems at various locations in all the global continents compared to a HFC404A configuration.

Due to the recent governmental regulations to limit the use of high GWP refrigerants, new lower GWP refrigerants are currently under evaluation by the industry. These new refrigerants exhibit promising thermal performance when compared to widely used refrigerants such as R404A. In this presentation, thermal properties and actual system performance data for non-flammable and mildly-flammable low-GWP refrigerants are discussed in details, showing energy efficiency and environmental benefits of using these new refrigerants in commercial refrigeration. In addition, changes in equipment design and control to further improve energy efficiency are explored, with focus on systems with moderate glide refrigerants.

It is well  know that when dealing with R744 high ambient temperatures can create design issues including loss of efficiency or reliability.  Currently a majority of the design effort is being focused on adapting the refrigeration circuit design to adapt to higher ambient conditions.  What if we could de-couple the impact of ambient temperature from the system entirely?  This seminar will explore a case study of an operating hybrid geothermal transcritical CO₂ installation from design, installation and  through first year of operation.

Refrigerants are essential to multitudes of HVAC&R processes in the commercial sector. Although meant to be contained within various equipment types, their usage inevitably leads to leakage, which may directly contribute to ozone depletion and/or global warming. In response, CO2 rose as a viable alternative in refrigerated beverage vending machines. Simultaneously, federal regulators continue to update minimum/high-efficiency standards for equipment efficiency, and are additionally exploring a proposal for prohibiting certain high-GWP refrigerants. This presentation will discuss the findings of a high-level evaluation, conducted by TTC, on the efficiency and performance of a CO2 vending machine and the applicable standards.

This presentation will cover the training needs for personnel involved installing and operating VRF systems, to include: Emphasis on skill requirements for successful install and operation of VRF systems compared to conventional systems, installation best practices, manufacturer specific training, and using manufacturer service tools for operation and maintenance. The presenter will also touch on manufacturer training available and how OEM service tools can be used for VRF system maintenance and ongoing commissioning.

This presentation will cover unique operations and maintenance characteristics of VRF systems that result in specific revised or additional tasks beyond the familiar needs of DX split systems. First there will be a brief overview the unique hardware, software and control technologies used in VRF systems that distinguish them from conventional DX split systems.  Next the seminar will highlight periodic operation & maintenance functions unique to VRF systems that must be incorporated in a maintenance program.

This presentation will look at the owner's VRF operation and maintainance (O&M) requirements at a hotel facility with multiple types of HVAC systems.  Presenter will discuss start-up of VRF systems, which replaced conventional systems  as part of a phased renovation.   Discussion will include: operations and maintenance requirements for VRF systems compared to conventional systems.  Presenter will discuss lessons learned from VRF system installation and start-up as it relates to facilities managers.

This presentation discusses aspects of VRF system operation, maintenance and repair that are unique to the HVAC service industry. The presenter explains how to avoid VRF failures through the proper care and feeding of a VRF system. While many maintenance tasks in VRF are similar to a convention system, there are differences that require a greater depth of knowledge on VRF.  A service contractor’s view and lessons learned.

Air leakage data from six parallel fan powered terminal units that utilized electronically commutated motors were evaluated to determine if simple models of air leakage could be developed for applications in building energy simulation programs. The data is from an earlier investigation by Edmondson et al (2011). Units with both 8 in. (20.3 cm) and 12 in. (30.5 cm) primary inlets from three manufacturers were evaluated. The analysis included the impact of downstream static pressure, upstream static pressure, and primary airflow on the leakage from the units.

Outdoor airflow rate, building static pressure, supply air duct static pressure and relief air plenum static pressure, as controlled variables, are maintained by modulating the speed of the supply and return fans and the position of the outdoor, recirculating, and relief air dampers in an air handling unit (AHU). In practice, the three dampers are interlinked completely or partially to match independent control inputs with the controlled variables. The traditional damper control has all the three dampers interlinked with no control over the relief air plenum static pressure. The reverse relief airflow might occur as the outdoor air damper approaches the closed position. To prevent the reverse airflow, one of solutions is to decouple the relief air damper and maintain positive static pressure at the relief air plenum. Two control methods are available based on the control loop design.

ASHRAE Grant-in-Aid Graduate Student Research Paper: This study presents a summary of experimental measurements on the airflow characteristics and pollution distribution around a non-breathing thermal manikin. The two objectives are: To examine the extent to which personal (body posture, clothing insulation, table positioning) and environmental factors (room air temperature and ventilation flow) affect the airflow characteristic (velocity and temperature) around the thermal manikin. To examine the pollution distribution within the convective boundary layer (CBL) around a thermal manikin and personal exposure to two types of airborne pollutants under factors that influence the CBL.

The development of spool compressors for various applications is investigated.  Using comprehensive modeling techniques it is shown how the various trade-offs in compressor design can be mitigated prior to extensive design and prototyping effort being expended.  The study focuses on air-conditioning applications and the practical limitations associated with the comprehensive modeling approach.

An in-depth analysis of the comprehensive model results of a spool compressor on various low-GWP refrigerants is presented.  The heat transfer, leakage, and frictional components are explored independently.  This analysis aims at demonstrating how the comprehensive modeling tools can be used to make more informed design decisions when comparing performance with various working fluids.

A simulation model to predict the performance of a prototype CO2 compressor is presented. This prototype compressor employs the Sanderson-Rocker Arm Motion (S-RAM) mechanism, which converts the rotary motion of the shaft into a linear reciprocating motion of the cylinders. The piston stroke can be variable by changing the incline angle between the connecting rod and compressor main shaft centerline. The compressor model is mainly composed of two main sub-models simulating the kinematics of the drive mechanism and the compression process. A valve sub-model is included in the compression process model.