Description

Optimizing Water Heating Heat Pump Configuration for Schools: A Comprehensive Guide

Determining System Requirements: Maximum Daily Water Consumption and Water Tank Selection

1. Application Scope

• Schools typically require hot water for student showers, toilet facilities, dishwashing in the cafeteria, and kitchen operations. However, specific needs can vary significantly from one educational institution to another.

2. Calculating Water Requirements

• Student Shower Hot Water: On average, a consumption rate of 35L per student per day is considered, assuming all students use hot water simultaneously.
• Bathroom Sink Hot Water: Approximately 5L per person per day is allocated for this use.
• Dishwashing and Kitchen Hot Water: Calculated at 10L per person per day, based on two meals served daily.
  Note: The hot water design is focused on essential needs such as bathing, face – washing, dishwashing, and kitchen vegetable – washing. Hot water for tasks like clothes – washing or mop – washing is not included. Schools should actively promote water conservation among students to ensure the efficient use of these precious resources.
  

  Real – World Examples: School Heat Pump Installations

  Xinzhan Town Central School in Southwest China

  Water Tank Calculation

  • School Background: This school has 922 students in total, with 144 living in dormitories. It requires sanitary hot water for student showers, face – washing, cafeteria dishwashing, and kitchen vegetable – washing. Considering future planning, development, and system standardization, meal – related hot water is projected for 1000 people, while shower and face – washing hot water is estimated for 200 people. The following table details the water consumption:
    

    Hot Water Demand Occasion	Water Users (person)	Consumption Amount(L)	Total (T)	Remark
    Canteen Sanitary Hot Water	1000	10	10	Fixed Amount
    Tap Hot water of Student Dormitory	200	5	1	Fixed Amount
    Student Shower Hot Water	200	35	7	Fixed Amount
    Total			18
    Tank selection			20

  

  Heat Pump Selections

  • Project Water Demand: The project requires up to 20 metric tons of domestic sanitary hot water. In winter, the lowest ambient temperature is 5°C, and the tap water temperature is around 10°C.
  • Heat Calculation: To heat 20 metric tons of tap water from 10°C to 55°C, we use the formula Q = CM△T. Here, Q = 1.1631(ton)(55 – 10)=52KWH for 1 ton of water. For 20T of water, Q = 20*52 = 1040KWH.
  • Heat Pump Capacity Adjustment: Air source heat pumps have a characteristic where the lower the outdoor temperature, the lower the heat output. When selecting a heat pump, its heat output must be adjusted according to different ambient temperatures. For example, when the ambient temperature is low, the capacity decreases. A single unit of PHNIX PASHW050S – XI has a heating capacity of 12KW, and two units of PHNXI PASHW100S – XI have a combined heating capacity of 24KW.
  • Working Time Calculation: The required working time N = 1040/60 = 17h.
  • Final Heat Pump Selection: Based on these calculations, the design incorporates one unit of PHNIX PASHW050S – XI and two units of PHNIX PASHW100S – XI to meet the school’s hot water needs efficiently.