Exhaust gas latent heat recovery device

A condensate economizer, comprising:

• a heat transfer tube disposed inside a duct through which exhaust gas flows, the heat transfer tube having a water supply inlet into which water to be heated for recovering latent heat of the exhaust gas is supplied and a water supply outlet through which the water to be heated is discharged;
• a water supply control part configured to control supply of the water to be heated to the water supply inlet;
• and
• a temperature sensor configured to detect an outlet temperature being a temperature of the water to be heated at the water supply outlet,
• wherein the water supply control part is configured to control supply of the water to be heated from the water supply inlet so that the outlet temperature is at a set temperature,
• wherein the heat transfer tube is disposed inside the duct so that the water supply inlet is positioned on a downstream side of the duct and the water supply outlet is positioned on an upstream side of the duct,
• wherein the set temperature is determined so that a condensate temperature of the exhaust gas is formed in a specific region of a middle section of the heat transfer tube disposed between the water supply inlet and the water supply outlet, wherein the heat transfer tube has a condensate region in which water vapor contained in the exhaust gas condenses;
• a dry region which is passed by the exhaust gas before reaching the condensate temperature upstream of the condensate region;
• and a dry-wet alteration region which is between the dry region and the condensate region, wherein the condensate region is formed in the specific region,
• wherein the duct includes:
• a first duct forming a bypassed passage;
• and
• a second duct forming a bypass passage bypassing the bypassed passage,
• wherein the latent-heat recovery device further comprises a damper for switching the bypassed passage and the bypass passage,
• wherein the heat transfer tube is disposed only in the bypass passage, and
• wherein a flow of the exhaust gas through the duct is configured to be switched so as to pass through either one of the bypassed passage formed in the first duct or the bypass passage formed in the second duct by the damper.