定流量冷冻水系统

Pump Sizing 水泵大小
• Select for full chiller flow 按冷冻机最大流量选择 • Head must be adequate for: 扬程必须足够
– – – – – Chiller evaporator 蒸发器 Longest circuit 最长回路 Coil 盘管 Three way valve 三通阀 Air separator 汽水分离器
BHP 56.23hp
But my time is valuable. Is there an easier way? 为了节省时间，有没有更简单 的方法。
ESP Plus
System Configuration 系统配置
2 @ 625 Tons
Supply 供水
Chiller Pumps 冷冻水泵 6G Constant Speed 定速 1500 GPM 75 Hp Each
90 80 70 60 Head 扬程
50 40 30
20 10 0 0 10 20 30 40 50 60 70 80 90 100
流体，百分比
Flow, Percent
What diameter impeller? 叶轮直径多少 What size motor do we need? 需要多大电机
Typical 3-way Valve Zone 典型三通阀和盘管
Terminal 终端负载 3-way control Valve 三通 控制阀
Balance valve 平衡阀 Supply 供水
Return 回水
Full Load Condition 满载情况
100 GPM @ 20 Ft
Chiller #2
Chiller #1
Return 回水
Constant Volume 定流量
Design Example, Future Conditions 例子，未来的情况
• Additional buildings are to be added to the system 系统内有新增的大楼 • Many building are currently short of chilled water 许多大楼目前都出现冷冻水量不足的情况 • Differential temperature across the chillers = 3.5 °F (The actual tonnage is: 3000 GPM X 3.5 °F X 500/12,000 = 437.5 tons) 通过冷冻机的温差为3.5 °F （实际上使用的吨数 为：3000 GPM X 3.5 °F X 500/12,000 = 437.5 吨)
• Trim the impeller based on measured values.
根据测量值修剪叶轮
Consider doing this: 可以考虑：
• Using multiple pumps. 使用多台水泵 • Using primary-secondary or primary-secondary-tertiary pumping. 使用一次侧－二次侧或者一次侧－二次侧－三次侧送水 • Using variable speed pumping. 使用变速送水
Constant Volume System Components 定流量系统部件
Circuit Setters Chiller #2
Chiller #1
Load 负载
Triple Duty Valves 三功能阀 Expansion tank
膨胀罐
3 Way Valve 三通阀
Rolairtrol 汽水分离器
Simple 简化 System Curve 系统曲线
HeadLoss1 Flow1 HeadLoss Flow 2 2
2
Simple System Head Curve 简化系统曲线
100
设 计 扬 程 ％
Percent of Design Head
• Let’s say, 1500 gpm and 125 feet 例如， 1500 gpm and 125 feet最适合
Required head 所需扬程
Required flow 所需流量
Friction Head Loss 摩擦扬程损失
hf = energy lost through friction expressed as fluid feet of head, feet of fluid 由于摩擦损失的能量
Section IV. Constant Volume Distribution 定流量系统
Hydronic System Components 液体循环加热系统部件
Expansion 压缩水箱 Distribution Piping 送水管路 Pump 水泵
Air Separator 气水分离器
Full Trim Impeller 原来的叶轮
Vr
Vs Vt
Impeller 叶轮 Blades 叶片
Rotation 转向
Vr = Radial Velocity 径向速度 Vt = Tangential Velocity 切线速度 Vs = Vector Sum Velocity 合成速度 （总速度）
– – – – Duty point with respect to BEP. Horsepower requirement. 马力需求 Efficiency. 效率 NPSHR. 汽蚀余量
• Estimate lifetime costs. 估算总成本
– Initial cost. 初始成本 – Annual operating cost. 每年运行成本
Pump Horsepower 水泵马力
PumpBaidu Nhomakorabea
Water Horsepower Brake Horsepower
水动力 轴功率
Water Horsepower
Flow x Head x SG 3960
水动力（WHP）＝流量（GPM）×扬程（ft）／3960
Pump
Flow x Head x SG 3960 x Brake Horsepower Flow x Head x SG 3960 x Pump
Analysis and selection 分析和选型
• Analyze the system: 分析系统
– determine head and flow. 确定扬程和流量
• Use software to narrow the choice. 使用软件缩小选择范围 • Evaluate individual pump curves for: 分别评价水泵曲线：
• • • • 总流量＝3000GPM 扬程需求＝125ft 设计的供水温度＝45℉ 设计的回水温度＝55℉
625 tons x 2 x 2.4 gpm/ton = 3000 gpm
How do I select a pump? 如何选择水泵
Always do this: 一般：
• Select the right pump type at good efficiency. 选择一台效率最合适的水泵 • Insure the system is hydronically balanced. 保证系统循环加热平衡
Load 负载
Triple Duty Valves 三功能阀 Expansion tank
膨胀水箱
3 Way Valve 三通阀
Rolairtrol 气水分离器
Design Example, Original Conditions 设计例子，最初的情况
• Two 625 ton chillers operating continuously, partially loaded, 10F delta tee. 两台625吨冷冻机连续运转， 部分负载，10 ℉温差 • Total capacity = 3000 GPM • Head requirement = 125 FT • Design supply water temperature= 45 °F • Design return water temperature = 55 °F
Future System Configuration 未来的系统
3 @ 625 Tons
Supply 供水
Chiller Pumps 冷冻水泵 6G Constant Speed 定速 1500 GPM 75 Hp Each
Chiller #3
Chiller #2
Chiller #1
Return 回水
L V f = friction factor 摩擦系数 hf f D 2 g L = length of pipe 水管长度
2
Darcy-Weisbach relationship
D = pipe diameter 水管直径 V = fluid average velocity, ft/sec (flow / pipe area) 流体平均流速 g = gravitational constant 重力加速度
全载盘管
100 GPM 20 FT 500,000 Btuh 20 FT 0 GPM 3-way valve closed 三通阀关闭 10 FT 100 GPM @ 30 FT 55 F
Unloaded Condition 未加载情况
Heat 热量
Source 供给
Load 负载
Heat 热量
Typical Electric Centrifugal Chiller 典型电子离心式冷冻机
Constant Volume System Components 定流量系统部件
Circuit Setters 平衡阀 Chiller #2 Chiller #1
Brake Horsepower
轴功率（BHP）＝流量（GPM）×扬程（ft）×比重／3960×水泵效率
Horsepower Required 所需马力
Flow Head SG BHP 3960 pump


15001251 BHP 3960 0.842
Terminal 终端负载
0 GPM @ 0 Ft
阀的压差 Valve P.D. = 10 Ft
100 GPM at 45oF
100 GPM at 55oF
Fully Loaded Coil Supply water temperature 供水温度 Design return water temp. 设计回水温度 Coil design flow 盘管设计流量 Coil design pressure drop 盘管压降 Load (flow x 10F x 500) 负载 Coil P @ design flow 盘管压差 Bypass flow 旁通管路流量 Bypass P 旁通管路压差 3-way valve pressure drop 三通阀压降 Pump flow and head 水泵流量和压损 Actual return water temp 实际回水温度 45F 55F
“…the right pump type…” “…正确的水泵类型能够
Consider: 考虑：
• Location 位置 • Space available 占用空间 • Maintenance requirements 维修条件 • Flexibility 灵活性 • Reliability 可靠性 • Hydraulic requirements 水压条件
Trimmed Impeller 已修剪叶片
Vs Vr Vt
Reduced Velocity 流速降低
Rotation 转向
Reduced Impeller Full 叶轮变小 Impeller 原来的叶轮 Looks like a 11 5/8” diameter impeller 看上去像115/8”直径叶轮