【DKV】DCD每日观点：你的蒸发冷却塔性能正常吗？

yi321yi 2019-11-05

展开全文

Gary Dicke是DHD制冷中心主任

由DCD中国授权DKV编译并发表于DeepKnowledge微信公众号。

一个常见的误解，减少冷却塔的运行负载“应该更容易达到更低的水温”。

我们英国的许多客户，在他们的数据中心内运营了多年的冷却系统后，已经切身感受到了设备工艺的变化。这些变化将改变对冷却系统的需求，在某些情况下，冷却系统能够应对新的冷却负荷增加或减少要求，但在其他情况下，在炎热的月份，冷却水温可能达到临界水平，而且在寒冷的月份会出现系统结冰，尽管热负荷减少，系统结冰可能导致能耗更高。

对于冷却系统，连接多个单元的水力平衡可能对总体性能产生影响，增加进入通道，内部或外部组件的更改、基本现有系统增加一些附属设备等等，都会导致冷却系统的性能下降。

经常性的误解

一个经常性的误解是，当减少冷却塔的运行负载时，“应该更容易达到较低的水温”，因为冷却塔的设备容量大于所要求的冷却负载。很不幸的是，结果往往出乎意料。如果负荷降低导致水流量降低，则冷却塔可能很快出现新的问题：在冷却塔内，较低的水流量将造成气流通过冷却塔中的干燥区域，从而降低空气与水换热的效率，从而导致高电机功率上升和冷却性能降低。

导致系统低效的运行并不是最近才发生的，一些老旧的工厂总是如此运营。在某些情况下，参与工厂的运行和设计的人员已经不再提供服务，导致项目上有价值的文件的缺失。如果不从可管理性和可靠性角度的角度来分析排序问题，在诸多需要完成的重要任务来说，解决冷却系统的节能性不属于优先考虑的事情。

如何解决问题

通过有效且快速的进行热力测试，提供有关流体和温度的信息，这些信息可以为实际的运行提供非常有价值的参考信息，并且如果热负荷随工艺需求而变化，在较长的一段时间内，也很容易地重复上述的测试工作。

将这些信息与设备和系统周围的物理环境结合起来，我们就能很快的确定，是否有可以改进冷却塔的热性能、改进操作原理、降低功耗或提高冷水温度的一些措施。

在某些情况下，解决方案只需要改变冷却塔的运行方式，这根本不需要任何成本，但可以节省1000英镑的运行成本。

测试过程

测试工作需要完成三件事。首先，进入冷却塔，确定所有关键系统的运行状况，建立一个完整的冷却系统的热力图。其次，安装测量装置来记录数据，并且有必要了解整个系统的热负荷分布和流量值。再次，与运营者进行沟通，了解他们是否遇到任何运营问题，以及这些问题的细节。

在收集了所有这些数据后，我们将准备一份详细的报告，其中包括测试数据和我们的调研问题。这些资料作为进一步讨论的基础，然后决定后续工作的开展方向。

节能增效和降低成本

对于目前已经运行的系统，完成一份完整的节能潜力改造清单及对应的成本报价，以改善热力性能，降低运行成本，或两者兼而有之。

在进行这些测试的过程中，我们发现了许多问题，包括不正确的操作理念、不恰当的管道尺寸、低流量问题、设备损坏、老旧系统影响性能等等。所有这些建议都有助于提高整体性能和降低运营成本。

英文原文

Is your evaporative cooling tower performing correctly?

Gary Dicker, DHD Cooling

Gary Dicker is director of DHD Cooling

It is a common misconception that running reduced loads over cooling towers ‘should make it easier to achieve colder water temperatures.'

A number of our UK customers who have operated cooling systems on their site for many years have seen changes in their process equipment. These changes will vary the demand placed on the cooling systems, and in some cases cooling systems are able to cope with the increased or reduced demand of the new cooling duties, but in other cases water temperatures can reach critical levels in the hot months, can freeze systems in the cold months and can also lead to higher overall power consumption, despite reduced thermal loads.

With cooling systems, the balance of flows across multiple units can have an effect on overall performance, the addition of access platforms, changes in the internal or external components, additional plant being placed local to the existing systems and so on, can all lead to performance degradation of cooling systems.

Common misconceptions

It is a common misconception that running reduced loads over cooling towers ‘should make it easier to achieve colder water temperatures,’ because the installed capacity is greater than the new cooling load requirements. Unfortunately this can often not be the case. If a reduction in load results in lower water flow then problems with cooling towers can quickly occur; low water flow over cooling towers will encourage the airflow to channel through dry areas in the towers, reducing the effectiveness of the air leading to high motor powers and lower performance.

It’s not just recent changes in systems that can lead to poor performance. Some older plants have just always run like that. In some cases the people that were involved in operating and designing the plant are no longer available, there is limited documentation available on the systems, and with the many other important tasks that people are required to do, getting to grips with the cooling systems from anything other than a regulatory and reliability perspective is not a priority.

How to overcome problems

Thermal testing can be done cost effectively and quickly, providing information on flows and temperatures that can give valuable information on the systems operating parameters, and can easily be done over an extended length of time, if heat loads vary with process demand.

Couple this information with the physical condition of the equipment and surrounding systems and we can very quickly start to identify whether there are changes that can be made to improve thermal performance, adjust operating philosophies, reduce power consumption or improve cold water temperatures

In some cases the solution only requires altering the way the cooling towers are operated, which can cost absolutely nothing but save £1,000s in operating costs.

The testing process

To undertake the test we do three things. We access the cooling towers, to identify the condition of all the critical systems, and build up a picture of the complete cooling system. We install measurement devices to log data for as long as necessary to find out the heat load profile and flow rates over the system. And we talk to the operators to find out whether they experience any operational problems and what those problems may be.

After gathering all this data, we prepare a detailed report which includes the test data and our findings as a basis of further discussion, and next steps are then determined.

Audit to improve performance & reduce costs

A fully priced and justified list of potential changes that can be made to a given system to improve thermal performance, lower operating cost, or both.

In the pursuit of these tests we have found many problems including incorrect operating philosophies, pipework sizing, low flow issues, broken equipment, old systems interfering with performance, to name but a few. All have led to recommendations that have helped to improve overall performance and or reduce operating costs.