Large commercial complexes are the core of urban commerce, and HVAC energy consumption accounts for 45–55% of total building energy use. This project designed a central HVAC heat-exchange station for a 120,000 m² complex in the Yangtze River Delta, achieving an 18% reduction in overall system energy consumption through SAMIT high-efficiency plate heat exchangers + variable-frequency pumps + intelligent control.
1. Project Background
Customer
A large commercial complex in the Yangtze River Delta with a floor area of 120,000 m², comprising four formats: retail, dining, cinema, and office.
Design Cooling Load
Summer peak 7000 kW (2000 RT), winter heat load 4500 kW. Cooling source: 2 × 1000 RT centrifugal chillers.
Design Requirements
- PHE pressure rating 1.6 MPa (high-rise)
- Pressure drop ≤ 40 kPa (energy-saving)
- Unattended year-round operation
2. Technical Solution
Two SAMIT BR0.5 plate heat exchangers (2 × 100% capacity) were adopted, handling heat exchange on the secondary chilled-water side and the secondary cooling-water side respectively. The primary/secondary isolation design reduces scaling risk in the chillers and facilitates zone control.
| PHE No. | Service | Primary Side | Secondary Side | Area |
|---|---|---|---|---|
| PHE-01 | Chilled Water System | 7/12 ℃ (chiller side) | 8/13 ℃ (user side) | 56 m² |
| PHE-02 | Cooling Water System | 32/37 ℃ (tower side) | 32.5/37.5 ℃ (chiller side) | 48 m² |
3. Process Flow
4. Implementation
- Design: Based on annual hourly load simulation of the building, a 2-unit PHE configuration was determined, with a reserved position for a future third unit.
- Equipment supply: 2 SAMIT BR0.5 PHEs + 4 matching VFD pumps + BA control cabinet.
- Commissioning: Phased commissioning with summer full-load and winter partial-load assessments; K value stabilized at 4500 W/(m²·K).
Design detail: The secondary side uses closed-loop circulation with expansion-tank pressurization, and the PHE provides physical isolation between primary and secondary water. Even if impurities enter the secondary (user) side due to renovation, the chillers remain unaffected, avoiding scaling in the condensers/evaporators.
5. Operating Results
Energy Saving
Overall energy consumption down 18%, saving 2.8 million RMB/year in electricity.
Equipment Protection
PHE isolation design; chillers required no descaling over 3 years.
O&M Efficiency
BA system ran unattended year-round; fault early-warning accuracy 96%.
6. Lessons Learned
The core of large commercial HVAC is system-level energy saving rather than single-equipment saving. SAMIT high-efficiency PHEs provide primary/secondary water isolation; combined with VFD pumps and climate-compensation control, this saves 15–20% more energy than traditional direct-cooling modes. We recommend introducing a "system-level" energy-saving approach at the design stage of new projects to avoid costly retrofits later.