Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ∼2250 K (adiabatic) and the high pressure steam temperature up to 900 K. This paper investigates the potential of harvesting this energy to produce additional electrical power using solid-state thermoelectric (TE) power generators placed into the gap between the flame temperature and the steam temperature. Three dimensional (3D) numerical model of a simplified TE module is developed. Different dimensions of fin added to the TE module were investigated to maximize the additional electrical power generation without sacrificing the boiler efficiency.

For the state of condensation in tube, liquid condensate separation in middle process can prolong the state of steam entrance region of higher heat transfer coefficient. It is called short-tube effect theory. Combined with the traditional condenser, a shell and tube condenser was designed for experiment research in this paper, and compared with the traditional condenser by opening liquid distribution pipes arranged in both sides of condenser. The results showed that liquid distribution pipes with different diameter have different condensation effect. Under the same steam flow rate of inlet, liquid distribution pipes with different combination of diameter and number indicated that its coefficient of heat transfer are higher than the traditional heat transfer by 14.2%, 15.5% and 25.1%. This result illustrated that heat exchange efficiency of a shell and tube condenser with liquid distribution pipes is better than a traditional condenser.

An approach to design multi-channel cylinder dryer was proposed. The heat transfer performance and flow characteristic under various structural parameters were analyzed. First, an experiment was designed and set up to measure the condensing heat transfer coefficient and the pressure drop in order to verify the applicability of the Cavallini’s correlation. Then, the relationship among the count of channels, aspect ratio, spacing ratio, width, height and hydraulic diameter of a channel was given. Finally, the correlation of condensing heat transfer and the homogeneous model were introduced in order to observe the heat transfer performance and flow characteristic of the multi-channel cylinder dryer affected by different structures. The study reveals that the structural parameters including count of channels, aspect ratio, spacing ratio of a channel dramatically influence the condensation heat transfer coefficient and frictional resistance of the steam. Based on the selected paper machine, it is suggested that the overall performance of the multi-channel cylinder dryer is best if the count of channels is 150–200, the aspect ratio is 1:3 and the spacing ratio is 1:1–1:3.

The clustering phenomenon on the solid wall during dropwise condensation is analyzed with reflection spectrum. From the theoretical prediction of the reflectivity for thin liquid films with different thickness on stainless steel surface, it is ascertained that the reflectivity corresponds to the coacervate characteristics of the steam molecular. Furthermore, the experimental data of the reflection spectrum during dropwise condensation in literature also demonstrated that the reflection feature and so as the coacervate characters lie between liquid and steam after the droplet departing during an actual continuous condensation process. The clustering model is used to analyze the results, indicating that clusters form on the blank surface. And it is found that different microstructures of the solid wall would lead to different deposition rates of the clusters, which prompts an effective way to enhance heat transfer process of condensation by accelerating the deposition rate of clusters with surface modification.

Experiment was conducted to study steam condensation in horizontal microchannel etched on silicon wafer and bonded by a Pyrex glass plate from the top. The trapezoidal microchannel had a top width of 7943.11μm and depth of 81.77μm with hydraulic diameter of 161.49μm. The experiments were performed at different steam mass fluxes ranged from 128 kg m −2 s −1 to 320 kg m −2 s −1 , while the inlet temperature of cooling water was fixed at 30°C or 50°C. Characteristics of condensation heat transfer and pressure drop in microchannels were measured and discussed. The temperature of Pyrex glass and local steam quality were also tested. It is found that the heat transfer flux, heat transfer coefficient and pressure drop depend greatly on steam mass flux and cooling water temperature.

At present, a microchannel heat exchanger is requested to achieve high efficiency in small size energy equipments. In order to clarify the heat transfer mechanism in a microchannel heat exchanger, knowledge on the thermal hydraulic characteristics of condensation flow in the channels is essential. However, study on the thermal hydraulic characteristics of condensation flow in a microchannel is hardly conducted except visualization of flow patterns. Objectives of the present study are to estimate the heat transfer performance of the present device and to observe the condensation behavior of vapor flow to clarify the thermal hydraulic characteristics of condensation flow in a capillary tube. As the results, it is confirmed that the microchannel heat exchanger realizes heat exchange of 7 kW when phase changes. In a single capillary glass tube as a simulated unit microchannel, the annular flow, the injection flow and the bubbly flow in a capillary tube are observed. According to the comparison of the present device and the glass tube experiment, it is suggested that the flow structure in the microchannel heat exchanger is almost same as that in the glass capillary tube.

In a steam-compression refrigeration cycle, optimum heat exchange efficiency is acquired and compressor liquid hammer can be avoided if “zero superheat” arises at dry-evaporator outlet. Therefore zero superheat control study is of value. since refrigeration cycle will not get stable while it tends to hunt nearby zero superheat, expansion valve-dry evaporator regulation loop have to run at a positive superheat; and no fit theory is able to guide the design on the stability of expansion valve-dry evaporator regulation loop until the cause of refrigeration cycle hunting is found. Flow display experiments reveal the mechanism that refrigeration cycle will hunt next to 0 superheat while vapor/liquid two phase flow alternates at expansion valve exit. on the ground that phases can be told apart by thermal sensing rather than superheat, a specialized sensor has been developed to detect 0 superheat signal which serves as the feedback signal of expansion valve-dry evaporator regulation loop, the experiment results prove that the thermal sensor can afford 0 superheat.