Detailed, building-integrated, dynamic thermal modeling of HVAC systems• From conventional HVAC to advanced systems• Flexibility for custom HVAC configurations and controls• Accounts for all gain/losses, heat transfer, and thermal mass in the building • Direct-interaction with building loads, bulk airflow/nat vent, and HVAC systems• Exceptionally well suited to modeling mixed-mode and building-integrated systems,
including double-skin facades and earth-tube thermal pre-conditioning
Some examples of HVAC systems and configurations possible• VAV systems with state-of-the-art controls, air and water supply temperature resets,
airside and waterside economizer/free cooling, demand-controlled ventilation, etc.• Highly tailored system controls and configurations• Dedicated outside air systems (DOAS) with fan-coils, chilled beams, etc.• Air-source heat pumps, DX cooling, and unitary cooling (split systems)• Indirect-direct evaporative cooling systems, desiccant-based air conditioning, etc.• Hybrid hydronic/air systems, radiant chilled/heated floors, ceilings, and panels• Displacement ventilation, underfloor air distribution, • Vented stack-effect double-skin facades, thermal labyrinths, and earth tubes• Mixed-mode systems with integrated control of mechanical and natural ventilation
Detailed modeling of building-integrated HVAC systems and configurations, using ApacheHVAC + MacroFlo + ApacheSim…• E.g., mixed-mode nat-vent + radiant cooling
Integrated thermal & energy analysis
6.41
4.51
3.64
1.93
0.26
3.85
4.13
4.19
0.64
0.36
0.36
0.49
0.21
VAV Baseline
VAV with WSFC
VAV+WSFC-precool
Radiant+DOAS
Cooling Season HVAC System Energy
Chillers (VAV only), cooling towers, and chilled water pumps (MWh)
Hydronic system pumps and evaporative cooling spray pump (MWh)
Fans (including cooling tower fan for waterside free cooling) (MWh)
Boilers, natual gas (MWh)
Estimated savings = 62 to 71%
May – September Denver, Colorado (TMY climate data)
Heating• Hot-water boilers (via part-load data or performance curves)
• Can serve space heating and/or domestic hot water• One or two boilers on a loop, with load threshold for sequencing• Storage losses for DHW• DHW loads can be met first by solar-thermal system
• Hot-water loop • Condenser heat recovery from any water-cooled chiller • Water-source-het pump for upgrade of recovered condenser heat• Constant- or variable-speed pumps on variable-flow loop
• Air-source heat pumps with backup heat sources• Heat pumps with constant-temperature ground-water or lake/ocean heat source• Custom heat source defined by part-load efficiency data, pump power curve, etc.• Combined heat & power systems• Airside heat-recovery devices (heat wheels, solid-syta• Heating coils – hot-water, electric, custom (heat rejection, regenerator for desiccant) • Hydronic heat – radiators, heating panels, fin-tube convectors, radiant slabs, etc. w
Components that can be modeled in ApacheHVAC VE 6.1.1
• One or two chillers on primary loop• Cooling tower model coupled to chiller
• Primary & secondary chilled water loops• Constant- or variable-speed pumps
• Cooling tower model and condenser water loops• Condenser heat recovery (heat pump COP for upgrade of recovered heat)• Waterside-economizer (non-integrated operation in VE 6.1)
• Custom cooling source defined by part-load COP data, outdoor WBT or DBT temperature dependencies, pump power data, fan power data, etc.
• Absorption chiller driven by HW boiler or custom part-load heat source• Direct-expansion (DX) cooling via pre-defined performance curves• Indirect and direct evaporative cooling• Airside coolth recovery – sensible, latent, enthalpy wheels, desiccants, etc.• Chilled-water cooling coils, induction units, and active chilled beams• Chilled ceiling panels, passive chilled beams, radiant cooling floor/ceiling slabs
Components that can be modeled in ApacheHVAC VE 6.1.1
• Supply, return, and exhaust (system- and zone-level)• Fan-powered boxes (series, parallel, hybrid, and underfloor)• Account for total static pressure and efficiency at flow rate
• OA, economizer, and mixing dampers• High-limit and differential enthalpy economizers• Fixed, scheduled, automated, or sensor-controlled min OA and make-up air• Face & bypass dampers—e.g., to track reduced TSP during bypass operation• Controlled percentage flow splitters• Calculation of ASHRAE 62.1 ventilation rates (table 6.3 method)
Humidity control• Spray chambers• Steam humidifiers• Enthalpy recovery• Desiccants—e.g., “uphill” moisture transport by heat-regenerated desiccant wheel• Differential enthalpy control of economizes and airflows
Components that can be modeled in ApacheHVAC VE 6.1.1
Controls for components and flow paths• On/off, time-switch/formula profile, deadband, and proportional controls
• Airflow rate, percentage flow, minimum outside air• Dry-bulb, wet-bulb, and dew-point temperatures• Heat transfer, moisture input, relative humidity, and enthalpy• Water flow rate & temperature (hydronic units)• Supply water temperature schedules and resets (e.g., per outdoor temp)
Sensor inputs to controllers
• Single-point and differential sensors (system-node, space, and outdoor conditions)• Flow rate• Dry-bulb, wet-bulb, and dew-point temperatures• Relative humidity• Enthalpy• CO2 concentration in a room or duct (e.g., for demand-controlled ventilation)
• Surface temperature (e.g., of actively heated or cooled floor/ceiling slabs)• Solar radiation on a surface of defined slope and orientation
• Formula profiles for time-switch controls can reference outdoor climate conditions.
Components that can be modeled in ApacheHVAC VE 6.1.1
Pre-defined systems require minimal user input, provide improved productivity • Controls for airflow rates, air and water supply temperature resets, dehumidification,
airside and waterside economizer/free cooling, demand-controlled ventilation, etc.• Autosizing of zone-level controller inputs, in addition to the system-level sizing of
fans, coils, and heating and cooling sources available for all ApacheHVAC systems• Ability to select/enter parameters for each system via a common AHU dialog
• DOAS vs. recirculating configuration• Coil leaving air temperatures• OA economizer high limits• Energy recovery device effectiveness and power
• Dialog-based revision of system control profiles• Operating schedules• Temperature setpoints and setbacks• Operational strategies for unoccupied hours
• Spreadsheet-based editing of sizing details, airflow requirements, and other options• Fully editable pre-defined configurations, controls, and equipment • An valuable starting point for building custom systems
Prototype systems in VE 6.1.11. Packaged terminal units
a) air-conditioning with DX cooling and hot-water boiler (PTAC) b) heat pump with DX cooling and air-source heat pump (PTHP)
2. Single-zone air-conditioning units (CV or VAV)a) DX cooling; direct-fired gas furnace heatingb) DX cooling; air-source heat pump, electric-resist. backup
3. Multi-zone VAV-reheat systems (can also run as CV) a) DX cooling and hot-water coils/boiler(s)b) DX cooling and parallel fan-powered (PFP) boxes with 2-stage electric re-heatc) Water-cooled chiller(s), chilled-water coils, and hot-water coils/boiler(s)d) Water-cooled chiller(s), chilled-water coils, PFP boxes with 2-stage electric re-heat
4. Dedicated outside air system (DOAS) a) Hot- and chilled-water (4-pipe) fan-coil unitsb) Active chilled beams and fin-tube convectors or radiators
5. Indirect-direct evaporative cooling VAV system, with HW reheat and CO2-based DCV
6. Mixed-mode system: integrated control of mechanical and natural ventilation/cooling
Additional prototype systems in VE 6.31. Coupling of 2-stage IDDE cooling SAT midbands
to space cooling set points2. Integration of setpoints in control profiles for
fenestration openings and HVAC airflow in mixed-mode mechanical plus natural ventilation/cooling system
3. Chilled and heated ceiling panels with DOAS4. Passive chilled beams with DOAS5. Dual-fan, dual-duct VAV with zone-level mixing6. Underfloor air distribution system
• UFAD supply air plenum thermal zone• Separate occupied and stratified zones• Heat-pipe to deliver dry, moderately cool air• Underfloor series/parallel fan-powered boxes• De-stratification of space with heating airflow• Fixed or variable-volume diffusers• Leakage path to return
• Enhanced modeling of chilled-water coils, loops, and chillers• Separate chilled-water loop + condenser-water loop and cooling tower• Up to ten chillers (separate chiller models) can be custom sequenced on each loop • Up to five user-defined load ranges for chiller sequencing• Waterside economizer mode (WSE) at loop level, plus separate “dedicated” WSE
• Advanced chilled-water cooling coil model• Autosize and detailed design input modes• Supports flexible chiller sequencing multiple coils on single waterside economizer• Foundation for pending
6.4 functionality• Autosizing of air-source heat pumps• Coupling of zone VAV controls for
linked vs. non-linked minimum airflow during night-cycle fan operation
• Specification of zone ventilation rates via thermal templates and room data in terms of cfm/person (l/s/person)
• Auto re-assignment of DX cooling COPper autosizing results for systems in PRM baseline models
• Automated (for PRM) and manual reporting of unmet load hours
• Library interface for importing and placing individual prototype HVAC systems• Stretchable multiplex boundaries• Enhanced hot-water loop modeling
• Sequencing for boilers and other water heating equipment (same as for chillers)• Primary-secondary and primary-only loops; constant and variable-speed pumps• Pre-heating via solar collector, condenser heat recovery, heat pump, and/or CHP
• Advanced hot-water heating coil model as foundation for other new functionality• Solar hot water model on hot water loop—i.e., for space heating and/or DHW• Improved air-to-air and air-to-water heat pump interfaces and configurations• Integrated waterside economizer operation with two configuration options
• Sharing heat-rejection cooling tower with chiller set• Dedicated cooling tower for WSE/chilled water pre-cooling
• Dry fluid cooler model on condenser water loop (heat rejection option)• Water-to-water heat-exchanger model with delta-T based variable effectiveness for
both WSE and additional pre-cooling options planned for 6.5• New solution procedure to support modeling of intentionally undersized heating and
