It is necessary to investigate the relative effect of various phenomena before neglecting the same for simulating the single-phase natural circulation loop to obtain an acceptable prediction. Hence, the present study focuses on the validation and effect of different assumptions related to Boussinesq approximation, property variation, bend effect, heat loss, axial fluid and wall conduction on the transient and steady-state characteristics. Effect of assumptions for different working fluids (water, brines and hybrid nanofluids), and assess the effect of different heat flux distributions, like uniform, linear, non-linear, sinusoidal and Gaussian, applied to heater are also explored. Mass flow rate (predicts heat transport capability), effectiveness (predicts heat transfer ability) and entropy generation rate (predicts irreversibility) are evaluated. The results disclose that the Boussinesq approximation with constant other properties under-predicts the steady-state mass flow rate and effectiveness and over-predicts the entropy generation rate. This assumption cannot be applied for all working fluids. The fluid and solid conduction is the crucial parameter for simulating transient characteristics. Gaussian heat flux distribution shows the highest mass flow rate and non-linear increasing heat flux shows the highest effectiveness and entropy generation rate. This study will help to consider reasonable assumptions for the numerical simulation.

为了模拟可接受的预测，有必要在忽略各种现象之前研究它们的相对影响。因此，本研究着重于与Boussinesq逼近，特性变化，弯曲效应，热损失，轴向流体和壁传导对瞬态和稳态特性有关的不同假设的验证和影响。还探讨了假设对不同工作流体（水，盐水和混合纳米流体）的影响，并评估了应用于加热器的均匀，线性，非线性，正弦和高斯等不同热通量分布的影响。评估质量流量（预测传热能力），有效性（预测传热能力）和熵产生率（预测不可逆性）。结果表明，具有恒定其他属性的Boussinesq逼近会低估稳态质量流量和有效性，而会高估熵产生率。该假设不能适用于所有工作流体。流体和固体传导是模拟瞬态特性的关键参数。高斯热通量分布显示最高的质量流率，非线性增加的热通量显示最高的效率和熵产生率。这项研究将有助于考虑数值模拟的合理假设。流体和固体传导是模拟瞬态特性的关键参数。高斯热通量分布显示最高的质量流率，非线性增加的热通量显示最高的效率和熵产生率。这项研究将有助于考虑数值模拟的合理假设。流体和固体传导是模拟瞬态特性的关键参数。高斯热通量分布显示最高的质量流率，非线性增加的热通量显示最高的效率和熵产生率。这项研究将有助于考虑数值模拟的合理假设。