在一项详细的实验室研究中，对无水箱盘管锅炉（家用循环热水器，其中一个翅片铜盘管已插入家用热水生产的锅炉水量）和一个带有外部热水换热器的家用锅炉的性能进行了评估。虽然还可以使用带有独立生活热水（DHW）“间接”水箱的供暖锅炉，并且具有更高的年效率，但无水箱盘管锅炉仍然是循环供暖市场的一个非常重要的组成部分，其优点包括成本较低和空间需求较小。在本项目中，按照标准协议对安装在锅炉中的普通无罐盘管的输出容量进行了评估。 在这些试验中，发现测得的容量低于标称容量。通过24小时模拟使用测试测量了这些系统的效率，发现在夏季仅DHW负载条件下，其效率在30.8%到40.8%之间。这种低负荷条件下的低效率源于需要持续保持较高的锅炉温度，以便在需要时输送DHW。评估了几种提高此类系统DHW生产效率的方法。其中之一涉及在泵送回路中使用外部板式换热器的新设计方法。研究发现，该系统在锅炉水和生活用水之间具有更好的热耦合，能够在较低的锅炉水温下产生更好的热量。 该系统还包括一个控制器，在没有家用热水供应的情况下，该控制器使锅炉能够降至室温。该系统的家用热水生产效率高达67%，但在长时间闲置后，DHW的输送存在时间延迟。这种类型的控制方法也用传统的无罐盘管锅炉进行了评估。引用:2020年虚拟会议论文

The performance of tankless coil boilers - residential hydronic heaters in which a finned copper coil has been inserted into the boiler water volume for domestic hot water production – and of a residential boiler with an external heat exchanger for hot water has been evaluated in a detailed laboratory study. While heating boilers with separate domestic hot water (DHW) "indirect" tanks are also available and have higher annual efficiency, tankless coil boilers remain a very important part of the hydronic heating market with advantages including lower cost and smaller space requirements.In this project, the output capacity of common tankless coils installed in boilers was evaluated following a standard protocol. In these tests, the measured capacity was found to be lower than the nominal capacity. The efficiency of these systems was measured over a 24-hour simulated use test and found to range from 30.8 to 40.8% under summer, DHW load only, conditions. The low efficiency under this low load condition derives from the need to maintain a high boiler temperature constantly to deliver DHW when needed.Several approaches to improve the DHW production efficiency of systems of this type were evaluated. One of these involved new design approaches with an external, plate-type heat exchanger in a pumped loop. This system was found to have better thermal coupling between the boiler water and the domestic water, enabling better heat production at lower boiler water temperature. The system also included a control which enabled the boiler to fall to room temperature in the case of no domestic hot water draw. This system was shown to have an efficiency for domestic hot water production as high as 67% but there is a time delay in DHW delivery after a long idle period. This type of control approach was also evaluated with conventional tankless coil boilers.